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Notes: During postnatal development of the pigeon, a large portion of the skeleton becomes pneumatized, displacing the hemopoietic bone marrow. The consequences of pneumatization on distribution and quantity of bone marrow as well as the availability of other sites for hemopoiesis have been investigated. Hemopoietic marrow of differently aged pigeons divided into five groups from 1 week posthatching (p.h.) up to 6 months p.h. was labeled with Fe-59 and examined by serial whole-body sections. Autoradiography and morphometry as well as scintillation counts of single bones and organs were also carried out. No sign of a reactivation of embryonic sites of erythropoiesis was found. Bone marrow weight and its proportion of whole-body weight increased during the first 4 weeks p.h. from 0.54% to 2.44% and decreased in the following months to about 1.0%. The developing bone marrow showed a progressive distribution during the first months of life, eventually being distributed proportionally over the entire skeleton, except for the skull. At the age of 6 months p.h. bone marrow had been displaced, its volume decreasing in correlation to increasing pneumaticity and conversion to fatty marrow. This generates the characteristic pattern of bone marrow distribution in adult pigeons, which shows hemopoietic bone marrow in ulna, radius, femur, tibiotarsus, scapula, furcula, and the caudal vertebrae.

Notes: Artificially incubated fertile eggs from wild alligators have a significantly better hatch rate than those of captive, pen-reared alligators, possibly due to differences in the morphology of the eggshells. We compared the morphology of eggshells of wild alligators to those of captive alligators living in semi-natural environmental pens. Lengths and widths of eggs were measured and volume was determined, assuming an ellipsoid shape. Eggs were also evaluated for the quality of the eggshell (the presence or absence of rough deposits). Pieces of shell were cut from unincubated eggs and from eggs incubated for 55 days (just before hatching) and examined by scanning electron microscopy. Open pores on the outer surface of the shells were counted and thickness of the pieces was measured from micrographs. Results indicated that the number of pores on eggshells was lowest in eggs of captive alligators with early embryonic death. The number of pores was intermediate in eggs with early embryonic death from wild alligators, and the number of pores was highest in eggs with full-term embryos from wild or captive alligators. It is suggested that decreased porosity of eggshells may be associated with early embryonic death, is more prevalent in captive animals, and may, therefore, be related to poor hatch rate among penreared alligators.

Notes: Adult hornets (Vespa orientalis; Hymenoptera, Vespinae) build the brood combs out of organic or mineral matter. The cement that serves to glue the building material together is secreted in their saliva, the latter hardening within seconds to form fibers or plates. This saliva-derived spittle overlies and unites the building particles laminally and vertically. The hornet larvae spin a cocoon within the brood cells, which is largely fastened to and supported by the cell walls and is composed of a network of silk fibers and interlinking flat surfaces. On the outside of the cocoon fibers are spherical button-like structures that are very rich in phosphorus. The chemical composition of the adult salivary cement and the larval cocoon fibers is similar: both contain the elements P, Mg, S, Cl, K, and Ca. The possible biological significance of these findings is discussed.Among social insects belonging to the Hymenoptera, there are three main groups that build a multitude of cells, namely, the paper wasps (Polistinae), the other social wasps or hornets (Vespinae), and the social bees (Apinae). The constructed cells serve mainly for rearing the brood, but in many instances (particularly among various Apinae) they also serve for storing honey and pollen. For building material, Apinae rely primarily on beeswax (a product secreted by the bee itself to which various amounts of plant resins are added). On the other hand, wasps (Polistinae and Vespinae) build mainly from matter collected in the nearby environment, be it organic matter such as tree bark, mineral matter, or a combination of the two.Much information has accumulated on comb and cell building among these insect groups (e.g., Wheeler, '23; Van der Vecht, '57, '65; Lindauer, '61; Michener, '61; Kemper and Döhring, '67; Wilson, '71; Guiglia, '72; Spradbery, '73; Edwards, '80; Brian, '83; Schremmer et al., '85). Species of Polistinae and Vespinae are prevalent in forest areas in Southeast Asia and in central and South America or in the temperate regions in both the northern and southern hemispheres, and they mainly use vegetable matter to build their combs. In contrast, species prevalent in the Mediterranean region, which is dry and relatively unvegetated during the wasp and hornet active season, rely more on nearby mineral than on plant matter. Comb building in the Oriental hornet is well known (Darchen, '64; Ishay et al., '67; Schaudinischky and Ishay, '68; Ishay, '73, '75a, b, '76; Ishay and Sadeh, '75, '76; Ishay and Perna, '79; Ishay et al., '82). Recently Ganor et al. ('86) described the cell wall in the V. orientalis comb, showing it to be composed of mineral particles collected near the subterranean nest, in contrast to the comb of two European species (V. crabro and Vespula) (Paravespula) germanica, which is built primarily of organic matter. Regardless of whether the building material is mineral or organic, the hornets utilize particles of sand or other minerals or pieces of wood wrapped and melded together by saliva. However, nothing is known about the cement or mortar used to glue together these “bricks.” The present investigation was initiated to increase our knowledge of this cementing substance.Combs of V. orientalis were collected from fields in the Tel-Aviv district in 1987 during the active season, which extends over most of the summer months. Because the combs are easily damaged, care was taken to remove them intact from the natural nest. Once removed, the combs were cleared of the existing brood (eggs, larvae, or pupae) and then stored carefully in dry glass vessels until examined. For the present study, combs were collected only from nests in Khamra soil, which is common in the Tel-Aviv district and along the coastal area of Israel. To investigate the morphology of the cement material in the comb, strips of comb wall as well as segments of the pupal silk dome were removed from each comb and prepared for examination. The comb wall strips were cut to a size of 3 × 6 mm and fastened to the stub of a scanning electron microscope (SEM). The silk pieces were processed in two ways: (1)strips of 3 × 4 mm were fastened onto a stub with the convex (outer surface) facing up or (2) with the concave (interior) side upward.Silk strips were boiled for 2 hours in distilled water to remove all impurities, such as foreign matter adhering to the silk secreted by the larvae. Examination of these silk fibres was carried out in the three ways: (1)SEM micrography of the exterior (white portion) of the silk dome; (2) micrography of the interior; (3) micrography of both exterior and interior aspects after boiling for 2 hours in distilled water to remove water-suspended foreign materials that may have clung to the silk dome in the course of ordinary nest activity.The chemical composition of selected specimens was investigated by x-ray analysis. They were done on JEOL 840 Scanning Electron Microscope (SEM) equipped with Link 10,000 Energy-Dispersive System (EDS). (With the EDS System, the spectrometer separates the elements according to energy rather than wavelength). Quantitative analysis was by ZAF4 program. Five strips of comb cell wall were examined from a randomly selected comb, each comb from a different nest. Micrographs were taken of isolated silk samples from each of the examined combs.

Notes: Dissections were performed to document buccal anatomy in three species of the pulmonate genus Helisoma Swainson, 1840. The 28 muscles which are responsible for radular feeding in these animals are organized in three concentric and integrated envelopes. The deepest of these includes muscles which manipulate the radula about the odontophoral cartilage. Elements of the middle envelope direct movements of the cartilage within the buccal cavity, and muscles of the outer envelope control movements of the buccal mass within the cephalic haemocoel. Motion analysis by videomicrography showed that muscles of the middle and outer envelopes contribute to the action of radular feeding by acting as antagonists to other muscles and to hydrostatic elements of the buccal apparatus. Observations of radular dentition showed that although each of the three species examined has a unique radula, especially with regard to the specific details of tooth shape, all resemble a radula characteristic of the Planorbidae with regard to other, more general, aspects of ribbon architecture.

Notes: Crocodilians and birds are the extant representatives of a monophyletic taxon known as archosaurs. Their limbs are highly derived in terms of reduction in number of skeletal elements in both the carpus and the tarsus. It is necessary to have a detailed description of crocodilian limb ontogeny to address the evolutionary issue dealing with the origin and organization of the avian limb. In this paper, we present an analysis of the early development of the crocodilian limb skeleton. Contrasting with earlier observations, we redefine the number and composition of carpal, tarsal, and phalangeal elements. This ontogenetic information is then used to introduce a revision of the homologies of the skeletal elements in the crocodilian limb. Some invariances are pointed out in the developmental organization of tetrapod limbs and this evidence serves to readdress several issues concerning the evolution of the avian limb. We present further embryological data in support of the hypothesis that digits 2-3-4 are the components of the wing skeleton in birds. In general, our comparative survey indicates that the elements that appear late in ontogeny are the ones lost in phylogeny. By comparing turtle (primitive) limb development with crocodilian and bird development, we propose a hypothesis in which the derived skeletal patterns found in crocodilians and birds have originated by a heterochronic process of paedomorphosis.

Notes: A unique pathway that utilizes endoplasmic reticulum (ER) networks is proposed for screening pigment granule formation in the retina of adult Eumesosoma roeweri. Smooth endoplasmic reticulum (SER) functions to transport pigment particles to the formative site. Each site is composed of concentric, interconnected rings of SER that are filled with dense-cored, spherical pigment particles. Formation of the screening pigment granule begins by the release of particles from the innermost rings of carrier SER. Continued release followed by fusion and condensation of the pigment particles results in the formation of a mature pigment granule.

Notes: Light and scanning electron microscopy of vascular replicas from the facultative air-breathing fish Heteropneustes fossilis show modifications in the macrocirculation of the respiratory organs and systemic circulation, whereas, gill microcirculation is similar to that found in typical water-breathing fish. Three and sometimes four ventral aortae arise directly from the bulbus. The most ventral vessel supplies the first pair of arches. Dorsal to this another aorta supplies the second gill arches, and a third, dorsal to, and larger than the other two, supplies the third and fourth arches and the air sacs. Occasionally a small vessel that may be the remnant of a primitive aortic arch arises from the first ventral aorta and proceeds directly to the mandibular region without perfusing gill tissue. The air sac is perfused by a large-diameter extension of the afferent branchial artery of the fourth gill arch and its circulation is in parallel with the gill arches. Blood drains from the air sac into the fourth arch epibranchial artery. A number of arteries also provide direct communication between the efferent air sac artery and the dorsal aorta. All four gill arches are well developed and contain respiratory (lamellar) and nonrespiratory (interlamellar and nutrient) networks common to gills of water-breathing fish. Air sac lamellae are reduced in size. The outer 30% of the air sac lamellar sinusoids are organized into thoroughfare channels; the remaining vasculature, normally embedded in the air sac parenchyma, is discontinuous. A gill-type interlamellar vasculature is lacking in the air sac circulation. Despite the elaborate development of the ventral aortae, there is little other anatomical evidence to suggest that gill and air sac outflow are separated and that dorsal aortic oxygen tensions are maintained when the gills are in a hypoxic environment. Physiological adjustments to hypoxic water conditions probably include temporal regulation of gill and air sac perfusion to be effective, if indeed they are so.

Notes: The antennae of adult Damalinia ovis, the sheep louse, were studied using light and scanning electron microscopy. Sensory structures are located on all three antennal segments with the predominant sensilla type being tactile. Nine different types of sensilla are described on the basis of external appearance. One of the sensilla, designated a “pit organ” because of its unusual shape, has not been described previously. A pair of these sensilla are present on each antenna, and their function is unknown. A group of 11 sensilla on the tip of each antenna contains olfactory and chemosensory pegs, and a possible thermohygroreceptor. The antennae are sexually dimorphic, the male having more tactile sensilla, two well-developed terminal hooks, and a different cuticular architecture on the posterior surface of antennal segment 1.

Notes: The formation of the unpaired structure ventral to the basibranchial region, the so-called urohyal, differs within osteichthyans. A cartilaginous preformed, unpaired “urohyal” is present in sarcopterygians. A three-tendon ossification is present in Polypterus. An “urohyal” or urohyal is absent in both Amia and Lepisosteus. The urohyal formed as an unpaired ossification of the tendon of the sternohyoideus muscle is a feature of teleosts. A new structure, the parurohyal, arises as a double ossification of the tendon of the sternohyoideus muscle in siluroids; during ontogeny an anterodorsal crest or cup-like structure derives from the anterior basibranchial region and the tendon bone; therefore, the parurohyal is compound in origin. Judging from their formation and their distribution within osteichthyans the cartilaginous preformed “urohyal” and the teleostean urohyal are nonhomologous, whereas the urohyal and parurohyal are homologous. The urohyal is connected by ligaments with the ventral hypohyals in most teleosts, whereas it articulates with the ventral hypohyals in teleosts such as Anguilla and Chanos. The parurohyal is a synapomorphy of siluroids. The parurohyal in siluroids is articulated with both ventral and dorsal hypohyals, and with the basibranchial region in catfishes such as diplomystids and ictalurids, whereas it articulates only with the ventral hypohyals in other catfishes such as trichomycterines. The passage of the hypobranchial artery through the hypobranchial foramen of the parurohyal is a unique feature of siluroids, like the absence of the basihyal bone.An ossified dorsal hypohyal appears late in ontogeny in Amia, as do tooth plates related to the medial side of the hyoid arch and branchiostegal rays in Amia, and tooth plates on the hyoid arch and branchiostegal rays in Elops (unique features within extant teleosts). Two ossified hypohyals, a synapomorphy of teleosts, are present early in ontogeny.There is intraspecific variation in the onset of ossification of the bones of the head, but the sequence of ossification between bones in a defined structural system is conserved (e.g., branchiostegal rays ossify first, then bones of the hyoid arch).

Notes: The vas deferens of Ambystoma macrodactylum is composed of a peritoneal epithelium, connective tissue layer with fibroblasts, circular smooth muscle, capillaries, cells containing lipid, and a luminal epithelium composed of a single layer of cuboidal cells covered by a net of interconnected ciliated squamous cells. The cuboidal cells have abundant rough endoplasmic reticulum, mitochondria, and PAS + secretory vesicles. Squamous cells of breeding males consistently have tufts of ∼100 cilia located at one end of the long axis of each cell. These cilia may help distribute secretory products. The squamous cells, absent in post-breeding males, are apparently sloughed into the lumen. Lipid vesicles are present throughout the cytoplasm of the cuboidal and squamous epithelial cells and are also in some cells of the connective tissue layer. These vesicles increase dramatically in number during the first 4 weeks after breeding and may serve as an energy pool for the next breeding season. Enzyme-histochemical tests for testosterone synthesis were negative. In addition to the accumulation of lipid and the loss of squamous cells in the vas deferens, after breeding PAS + vesicle production is terminated. These alterations appear to represent energy conservation strategies employed by the sperm-depleted vas deferens.

Notes: The concept of parallel muscle combinations, in which spindle density is significantly higher in small muscles compared to their larger counterparts in large-small muscle combinations acting across a joint, is supported by the results of this study regardless of the joint. Analysis of the canine data as well as previously published guinea pig forelimb and human pelvic limb data revealed no significant difference in spindle density between antigravity and non-antigravity muscles. Furthermore, a gradual increase in spindle density from proximal to distal on the limb was not found, although spindle density was significantly higher in the intrinsic manus or pes muscles compared to more proximal limb muscles in all three species. The significant differences in spindle densities in parallel muscle combinations and in manus/pes versus proximal muscles are discussed relative to their possible role in the control of locomotion.

Notes: The choanocyte chambers of eight different haplosclerid sponge species have been investigated with regard to their histological structure, their relation to the mesohyl, and their arrangement between the canal systems. Two fundamentally different organizational types occur in the investigated sponge species. In Haliclona rosea, H. oculata, H. elegans, H. simulans, H. rava, H. fistulosa, and Acervochalina limbata the choanocytes are separated from the mesohylar tissue, being more or less covered over the outer surface by pinacocytes belonging to the incurrent canal walls. In Haliclona indistincta, on the other hand, the choanocytes are, as in most other Demospongiae, in contact with the mesohyl at their outer surfaces. This indicates that the present order Haplosclerida is polyphyletic and contains sponges of a presumably poecilosclerid origin.

Notes: The three-dimensional structures of the carotid labyrinth in five species of anurans representing four families (Rana nigromaculata, Rana catesbeiana, Bufo japonicus, Hyla arborea, and Xenopus laevis), and three species of caudates representing three families (Cynops pyrrhogaster, Hynobius nebulosus, Ambystoma mexicanum) were compared using vascular corrosion castings and scanning electron microscopy (SEM). Anuran carotid labyrinths are spherical in shape and are classified into two groups according to the origin of the external and internal carotid arteries. One group, which included Rana, Hyla, and Bufo, is characterized by the presence of a vascular ring at the proximal end and some vascular routes at the distal end of the labyrinth. The external and internal carotid arteries originate from these structures. The other group, which includes only Xenopus, is characterized by the external carotid artery opening directly from the central chamber or the common carotid artery, and by the internal carotid artery originating from within the vascular maze. The vascular maze is most complex in Xenopus, less so in Rana and Bufo, and simplest in Hyla. The carotid labyrinths in Cynops and Hynobius are oblong in shape. The fundamental organization in salamanders is similar to that in anurans. The vascular maze, however, is much simpler than in Hyla. There is no specialized swelling in Ambystoma mexicanum. The present findings suggest that most amphibian carotid labyrinths have the appropriate architecture for controlling vascular tone.

Notes: The vomeronasal sensory epithelium of a crotaline snake, Trimeresurus flavoviridis, was shown to consist of a superficial supporting cell layer and an underlying sensory cell layer composed of columns of sensory cells. The supporting cell layer consists of both supporting cells and dendrites of the underlying sensory neurons. The apical regions of sensory cell dendrites contain numerous microtubules, many elongated mitochondria, centrioles, and electron-dense bodies. The dendrites terminate as dendritic knobs from which microvilli project into the vomeronasal lumen. Smooth vesicles are abundant in the dendritic terminals and their vicinity. Supporting cells also bear microvilli, and these cells contain large electron-opaque granules and dense vesicles near their free surfaces. Cytoplasmic extensions of the supporting cells form a meshwork which separates dendrxites from each other in the vicinity of the luminal surface. The meshwork becomes obliterated in the infranuclear region of each supporting cell. Bipolar-shaped sensory cells with lightly stained round nuclei contain the characteristic cell organelles of neurons and are thought to be sensory neurons. These cells are especially characterized by well-developed lamellae of rough endoplasmic reticulum and extensive arrays of smooth endoplasmic reticulum. The perikarya of cells located in the apical region of the cell columns tend to contain larger amounts of smooth endoplasmic reticulum and lipofuscin granules than the perikarya of cells located in lower regions. Undifferentiated cells are found in the basal region of the columns. Satellite cells form the framework of the columns and are also found among neuronal elements.

Notes: The protandric hermaphrodite Ophryotrocha puerilis possesses one pair of eyes. They are located in the peristomium. Each light-sensitive organ consists of one sensory cell and one to two supporting cell(s) embedded in a cup-shaped reflector. The sensory-supporting cell complex is enveloped by a basal lamina. This lamina is supposed to be identical with the neural lamella. Thus the eyes proper have to be regarded as protrusions from the brain, while epidermal cells seem to differentiate to crystalline cells (reflector) and are deposited onto the sensory complex.The reflector is built up by several cup-shaped cells (juveniles, 4-5; adults, 10-12). Each of these cells comprises a multilayer of parallel-oriented, membrane-bound crystalline platelets which are thought to be guanine. The sensory cell is of the inverted rhabdomere type. Submicrovillar cisternae, typical for most polychaete eyes, are lacking. The first and always present supporting cell entirely envelops the sensory cell, thus forming the extracellular space around the rhabdomere. It does not contain any pigment granules. Often but not always a second supporting cell has been observed surrounding the sensory cell and first supporting cell. It is interpreted as a glial cell.In the sensory cell beneath the rhabdomere, pino- and phagocytosis can be observed and secondary lysosomes are found in high densities. Preliminary results seem to demonstrate that there is no distinct diurnal cycle of receptoral membrane recycling. In comparison with the ocelli of Dinophilidae, which have been interpreted as a dorvilleid-related family, morphological differences and their application to phylogenetic considerations are discussed.

Notes: The appearance pattern of pharyngeal tooth germs was investigated in the larval Japanese dace, Tribolodon hakonensis, which has a bilaterally asymmetrical dentition. Teeth develop in a series of replacement waves beginning with the initial central tooth (Ce) and continuing with teeth of anterior (An) and posterior (Po) positions relative to the initial one. Identified by wave number (n) and tooth position (r), according to the formula n-1[r], tooth germs appeared in the order of tooth 0[Ce0], 1[Po1], 1[Anl], 2[Ce0], 2[An2], 3[Po1], 3[An1], 4[Ce0], 4[An2], 5[Po1], 5[An1], 5[An3], 6[Ce0], 6[An2] during the larval period. Dentition on the right side, however, lacks the first tooth at position An2 (tooth 2[An2]) and teeth at position An3. Tooth germs on the first, second, and third replacement waves appeared simultaneously on the arches of both sides. During following waves, tooth germs on the left side appeared later than those on the right. Delay of tooth germ appearance On the left side is interpreted as an inhibitory influence of existing tooth germs in accordance with Osborn's (Proc. R. Soc. Lond. Ser. B 179:261--289, '71) theory. The delay of tooth germ appearance on the left arch is most pronounced on the seventh replacement wave. Teeth of the right major row in adults of this species are replaced more frequently than those of the left major row, apparently in correlation with the absence of the first larval tooth at position An2 and teeth at position An3. It is hypothesized that cyprinids evolved the minor rows and specialized teeth of their adult dentition as apomorphic characteristics by the process of neoteny.

Notes: Development of the internal structures of the caudal region (muscles, bones, cartilages, nerves, and blood vessels) of the Da/Da mutant medaka and of wild-type +/+ fish was compared. Muscles and nerves were immunochemically stained by using an antibody to troponin T and antibodies to neurofilament proteins, respectively. Bones and cartilages were stained with alizarin red and alcian blue. In stages 31-32 of the Da/Da embryo, the rudiments of epurals 1, 2, and 3 differentiated dorsally opposite the sites of the ventral rudiments of the parhypural, the lower hypural plate, and the upper hypural plate, respectively. In the +/+ embryo, the rudiments of epurals 1 and 2 differentiated in the later developmental stages (after stage 34), but the rudiment of epural 3 did not differentiate. In the Da/Da embryo, the deep dorsal flexor passed dorsalwards and ended at the rudiment of epural 2, whereas the muscle passed ventralwards and ended at the rudiment of the upper hypural plate in the +/+ embryo. In the Da/Da fry, the epichordal region of the caudal fin fold grew and the notochord extended straight into the tail without bending, while in the + /+ fry, the epichordal region did not grow and the notochord turned dorsalwards within the tail. In the Da/Da fry, extra skeletal rudiments and musculature differentiated in the epichordal region of the caudal fin, whereas these supernumerary structures did not develop in the +/+ fry. The pattern of the epichordal skeleton and musculature in the caudal region of the adult Da/Da fish was an almost mirror-image duplication of the hypochordal structures. These observations suggest that the characteristic expansion of the dorsal fin and epichordal lobe in the caudal region of the adult Da/Da fish is due to a process of ventralization, whereby the dorsal skeleton, musculature, and fin fold are stimulated to differentiate in a pattern like that which is restricted to the anal fin and hypochordal lobe of the wild type.

Notes: Tongue musculature in 24 genera of snakes was examined histologically. In all snakes, the tongue is composed of a few main groups of muscles. The M. hyoglossus is a paired bundle in the center of the tongue. The posterior regions of the tongue possess musculature that surrounds these bundles and is responsible for protrusion. Anterior tongue regions contain hyoglossal bundles, dorsal longitudinal muscle bundles and vertical and transverse bundles, which are perpendicular to the long axis of the tongue. The interaction of the longitudinal with the vertical and horizontal muscles is responsible for bending during tongue flicking. Despite general similarities, distinct patterns of intrinsic tongue musculature characterize each infraorder of snakes. The Henophidia are primitive; the Scolecophidia and Caenophidia are each distinguished by derived characters. These derived characters support hypotheses that these latter taxa are each monophyletic. Cylindrophis (Anilioidea) is in some characters intermediate between Booidea and Colubroidea. The condition in the Booidea resembles the lizard condition; however, no synapomorphies of tongue musculature confirm a relationship with any specific lizard family. Although the pattern of colubroids appears to be the most biomechanically specialized, as yet no behavioral or performance feature has been identified to distinguish them from other snakes.

Notes: Wall and internal organelles of the encysting salt marsh heterotrich ciliate Fabrea salina were examined by bright field and Nomarski interference contrast microscopy and by transmission and scanning electron microscopy. A mucoid sheath believed to be derived from bacteria covers the ectocyst. The possible bacterial origin of this sheath has been demonstrated experimentally by its removal and reappearence after 24 hours. Control ectocyst maintained in sterile seawater did not replace the sheath. The ectocyst has a crinkled appearance. The endocyst is composed of two layers. The inner endocyst material is continuous with that of the plug located at one end of the cyst. The two membranes are separated from one another by an interwall space filled with fibrous material. The cytoplasm, covered by an outer double membrane pellicle, contains mucocysts, pigment granules, microtubules, non-ciliated kinetosomes, Golgi complexes, ribosome-studded endoplasmic reticulum, and mitochondria. The endoplasm contains numerous autophagosomes, mitochondria, and food reserve materials. The macronucleus is centrally located in the cytoplasm of the encysting organism.

Notes: Analysis of lateral and dorsoventral radiographic films shows that ingestion, transport, and mastication in Pedetes capensis (Rodentia) are cyclic and their movement patterns are essentially similar for the three food types offered. During the ingestion cycle, closing of the mouth is accompanied by a backward translation of the condyles, so that movement is predominantly orthal. During the opening stage, the extent of the anterior condylar translation is smaller. As a result the mandibular incisors move ventrally and posteriorly. During the ingestion cycles, food is transported to the back of the tongue, with the transverse rugae and the folds of the upper lip playing important roles.Springhares show a bilateral masticatory pattern; food is chewed on both sides simultaneously. During chewing, the condyles lie in their most forward position at maximum opening of the mouth. The mouth is closed by rotation of the lower jaw around the temporomandibular joint coupled with posterior condylar translation. At the beginning of the slow-closing stage, the upward rotation of the mandible slows and the jaw slowly shifts forward. During the grinding stage, the mandible is shifted forward with both toothrows in occlusion. During the opening stage, the jaw returns to its starting position.Comparison of kinematic and anatomical data on rodent mastication suggests that some dental characteristics form the most important factors regulating the masticatory pattern and consequently allow reasonably reliable prediction of rodent masticatory patterns.

Notes: Avian embryos can be completely paralyzed by injection of neuromuscular-blocking agents. We used a single injection of decamethonium iodide to paralyze embryos at 7, 8, or 10 days of incubation and analyzed the growth of individual bones (clavicle, mandible, ulna, femur, tibia, humerus) and of individual muscles that act upon some of those bones (clavicular and sternal heads of m. pectoralis, and mm. biceps brachii, depressor mandibulae, pseudotemporalis, and adductor externus). Growth of the bones is not equally affected by paralysis. Only 27% of clavicular growth (by mass) but 77% of mandibular growth occurred in paralyzed embryos, whereas the four long bones exhibited 52-63% of their normal growth. Analysis of muscle weight, fiber length and physiological cross-sectional area (weight/fiber length) indicate that there was greater reduction of the muscles acting on the limbs than of those acting on the mandible, i.e., diminished growth of the skeleton is correlated with reduced muscular activity. Specific retardation of clavicular growth is due to fusion of sternal rudiments and collapse of the thorax, as well as virtual absence of the musculature that normally attaches to the clavicle. We discuss these results in the light of intrinsic and extrinsic factors governing growth of tne embryonic skeleton. Paralysis reduces skeletal growth by reducing both the movements taking place in ovo, and the loads imposed on the bones by muscle contraction, changes that represent alterations in the mechanical environment of the skeleton.

Notes: This study using light and electron microscopy indicates that the saccus vasculosus is distinguishable in 9-mm embryos and grows continuously throughout embryonic development to the adult stage. In the saccus vasculosus, epithelial mitoses are observed in all stages studied. Phases of centriologenesis, ciliogenesis, and globule formation have been characterized in developing coronet cells. During the phase of centriologenesis, new centrioles appear in association with pre-existing centrioles and not on deuterosomes. After ciliogenesis, each cilium differentiates to a globule almost at the same time as the other cilia of the coronet cell. The inner membrane system of the globules seems to derive from the ciliary plasma membrane. This membrane system often produces membrane whorls during the development. The different phases of coronet cell development have been found in the same individual and in all the stages studied except the 9-mm embryo. Cerebrospinal fluid-contacting neurons are observed in the saccus epithelium from the 12-mm embryos on and are distinguishable from coronet cells in their early formative stages. The three cell types of the saccus vasculosus increase continuously in number during development. Nerve processes are found in the saccus vasculosus of embryos, whereas differentiated synapses appear later in the fry. The significance of continued coronet cell formation is discussed in relation to a putative coronet cell and/or a globule renewal cycle in the adult.

Notes: Changes of architecture of adult rat gastrocnemius medialis muscle (GM) due to growth were studied in relation to length-force characteristics. Myofilament lengths were unchanged, indicating constant sarcomere length-force characteristics. Number of sarcomeres within fibers was unchanged as a consequence of growth, allowing persistence of differences between proximal and distal fibers in all age groups. Distal fiber length at muscle optimum length was shorter for the 14- than for the 10- and 16-week age groups despite a lack of difference of number of sarcomeres. This is indicative of a shift of optimum fiber length with respect to muscle length to lengths higher than optimum length. Some evidence for the occurrence of distribution of fiber optimum lengths with respect to muscle optimum length was found in other age groups as well, albeit of a smaller magnitude. Muscle and aponeurosis length increased substantially with growth. Functional effects of increased aponeurosis lengths were increased contributions to muscle length changes by the aponeurosis, allowing smaller fiber contributions in older animals. Fiber angle increased approximately 5° with growth. Despite the differences of architecture indicated above, muscle length range between optimum length and active slack length was constant. This was probably caused by widening of this length range in the youngest age group by variations of architecture within the muscle. It is concluded that adaptation of aspects of muscle architecture is an important mechanism for adult muscle growth in rat GM. Of these aspects regulation of muscle length seems a dominant factor.

Notes: A light and electron microscopic study of the skin of domestic chickens, seagulls, and antarctic penguins revealed abundant extracellular dermal lipid and intracellular epidermal lipid. Dermal lipid appeared ultrastructurally as extracellular droplets varying from less than 1 μm to more than 25 μm in diameter. The droplets were often irregularly contoured, sometimes round, and of relatively low electron density. Processes of fibrocytes were often seen in contact with extracellular lipid droplets. Sometimes a portion of such a droplet was missing, and this missing part appeared to have been “digested away” by the cell process. In places where cells or cell processes are in contact with fat droplets, there are sometimes extracellular membranous whorls or fragments which have been associated with the presence of fatty acids. Occasionally (in the comb) free fat particles were seen in intimate contact with extravasated erythrocytes. Fat droplets were seen in the lumen of small dermal blood and lymph vessels. We suggest that the dermal extracellular lipid originates in the adipocyte layer and following hydrolysis the free fatty acids diffuse into the epidermis. Here they become the raw material for forming the abundant neutral lipid contained in many of the epidermal cells of both birds and dolphins. The heretofore unreported presence and apparently normal utilization of abundant extracellular lipid in birds, as well as the presence of relatively large droplets of neutral lipid in dermal vessels, pose questions which require a thorough reappraisal of present concepts of the ways in which fat is distributed and utilized in the body.

Notes: Development of neurons in the area triangularis of Gallotia galloti was investigated in Golgi-impregnated brain tissue. Four major neuronal types present in adults were found to originate from two migratory neuroblast types, which were followed from embryonic stage S.32. One type has a thick main medial process, whereas the second type has a long main lateral process. As they migrate toward the periphery of the nucleus, morphological characteristics of maturation appear, including growth cones, filopodia, and outgrowth of axons. Neuroblasts with a main lateral process differentiate into two immature neuronal types, bipolars and pyramidals, observed at S.33 and thereafter. The neuroblasts with a main medial process undergo some somatic translocation through a transitory tangential shaft. Then they develop into monopolar immature forms with a long varicose medial, process, appearing from S.36. onward. Immature bipolar neurons do not experience great changes in their dendritic arborization during development to the adult stage, but pyramidals and monopolars undergo a rapid development of the dendritic tree after S.36. By S.38 archetypes of adult neuronal forms are established. Hairlike appendages first appear on neurons at S.36 They decrease suddenly in S.38 and then proliferate in S.39 when spines first appear. Around the time of hatching, the hairlike appendages begin to disappear and spines become established. Reduction of spines occurs after hatching and continues to the adult stage. Possible influences of several external factors on neuronal maturation are discussed.

Notes: The female reproductive system of Sphaerodema rusticum consists of a pair of ovaries, two lateral oviducts, a median common oviduct, and a median spermatheca. Accessory glands are absent. Each ovary has five free ovarioles branching from the oviduct. Each ovariole consists of a terminal filament, germarium, vitellarium, brown mass, and an exceptionally long pedicel. The terminal filament consists of a central core, interstitial cells, and an outer sheath. In the germarium, which consists of trophic and prefollicular regions, the trophic region or nurse cell chamber is divided into four histologically differentiated zones, distinguished as zones I-IV. Nutritive cords, originating from the posterior end of the trophic core in zone IV extend centrally and join the developing oocytes in the prefollicular chamber and the vitellarium. The compact prefollicular tissue at the base of the trophic core gives rise to prefollicular cells which, after encircling the young oocytes, become modified into follicular epithelial cells, the interfollicular plug, and epithelial plug. The young oocytes descend into the vitellarium and gradually develop into mature oocytes. A compound corpus luteum is observed simultaneously in all the ovarioles of both ovaries after ovulation. Below the epithelial plug there is an accumulation of material, the “brown mass,” which develops cyclically in correlation with the ovulation cycle. Each pedicel stores five mature chorionated eggs ready for oviposition. The epithelium of the anterior region of the pedicel secretes a PAS-positive material. General morphology and histology of the subdivisions of the ovarioles are described.

Notes: The feeding mechanisms of two labrid fishes (Cheilinus chlorurus and C. diagrammus: Labridae: Perciformes) are modeled using four-bar linkage theory from mechanical engineering. The actions of the feeding mechanisms are simulated by a computer program that uses morphometric data to calculate the geometry of mechanism structure. The predictions of three different four-bar linkages regarding the kinematics of feeding are compared to the movements observed through hign speed (200 fps) cinematography. A previously unidentified four-bar chain was found to be an accurate model of the mechanism by which upper jaw protrusion, maxillary rotation, and gape increase occur in Cheilinus. This mechanism involves the anterior jaws including the mandible, maxilla, premaxilla, palatine, and suspensorium. The accuracy of two previously described four-bar linkages was also tested by comparison of model predictions and film results. The opercular linkage proposed by Anker ('74) as a mechanism of jaw depression via opercular levation was found to be a poor predictor of feeding movements. This four-bar chain involves the opercle, suspensorium, interopercle, and mandible. Muller ('87) proposed a mechanism of hyoid depression involving cranial elevation due to epaxial muscle contraction as input motion The links in this mechanism include the neurocranium and hyomandibula, hyoid, sternohyoideus muscle, and pectoral girdle. This model was an accurate predictor of hyoid depression in Cheilinus when simultaneous cranial elevation and sternohyoideus contraction were simulated. Quantitative kinematic models involve simplifying assumptions when applied to complex musculoskeletal systems, but such models have a wide range of applications to vertebrate functional morphology.

Notes: The morphology of both the main nasal cavity and the vomeronasal organ differs among species representing six families of caecilians. The main nasal cavity is either divided or undivided. The vomeronasal organ differs in position (mediolateral, lateral), size (large vomeronasal organ in the aquatic species), and shape (mediolateral extension, vomeronasal organ with a lateral rostral projection). The great amount of respiratory epithelium of the main nasal cavity, the large vomeronasal organ, and its extensive innervation in typhlonectids may reflect both phylogeny and habitat adaptation, for these taxa are secondarily aquatic or semiaquatic and have several concomitant morphological and physiological modifications. The vomeronasal organ is associated with the caecilian tentacle as the tentacular ducts open into it. This association is further evidence for the involvement of the caecilian tentacle in vomeronasal chemoperception and may represent the mechanism by which these animals smell though the main nasal cavity is closed during burrowing or swimming. Labelings of primary olfactory and vomeronasal projections by means of horseradish peroxidase reaction reveal that the pattern of vomeronasal projections is similar in Ichthyophis kohtaoensis, Dermophis mexicanus, and Typhlonectes natans, even though T. natans possess stronger vomeronasal projections relative to olfactory projections than I. kohtaoensis and D. mexicanus. However, there are differences with respect to the patterns of olfactory projections. The olfactory projection of I. kohtaoensis is characterized by many displaced glomeruli. T. natans has the smallest olfactory projection. The nervus terminalis is associated with the olfactory system as shown by selective labelings of olfactory projections.Six characters potentially useful for phylogenetic analysis emerge from this study of comparative morphology. The characters were subjected to analysis using PAUP to see (1) if any resolution occurred and (2) if any groups were distinguished, whether they corresponded to phylogenetic arrangements based on other morphological characters. The characters are too few to produce nested dichotomous sets for all cases, but they do support the two typhlonectid genera examined and Dermophis and Gymnopis as sister taxa discrete from other groups, and they show that species within genera cluster together.

Notes: A kidney from the budgerigar (budgie, parakeet; Melopsittacus undulatus) is composed of cortical reptilian-type nephrons (without loops of Henle) and mammalian-type nephrons (with loops) grouped together in medullary cones. The loop of the mammalian-type nephrons has a descending segment composed of thin and highly interdigitated cells. These thin limb cells have few mitochondria (15% of cell volume), undetectable Na+, K+-ATPase activity, and virtually no basolateral surface amplification. Prior to the hairpin turn, the descending limb thickens, but the cells continue to lack basolateral amplification. Cells just prior to and within the hairpin turn resemble cells of the entire ascending limb. These cells are thick (there is no thin ascending segment in the avian loop), with extensive infoldings of the basolateral membrane surrounding numerous mitochondria (45% of cell volume). The area of basolateral membrane is 25 times that of the apical membrane. The basolateral membrane (but not the apical membrane) is enriched in Na+, K+-ATPase activity. The structure of the avian mammalian-type nephron (as epitomized by the budgie nephron) and the fact that NaCl accounts for over 90% of the osmotic activity of avian urine leads to the conclusion that the countercurrent multiplier of the avian kidney functions by active NaCl transport from the entire ascending limb. No explanation is offered for the transport specializations found in the thick descending segment of the loop, just prior to the hairpin turn.

Notes: The cells-of-origin and the mode and site of termination of the interhemispheric connections passing through the anterior and posterior pallial commissures in the telencephalon of two lizards (Podarcis hispanica and Gallotia stehlinii) were investigated by studying the anterograde and retrograde transport of unilaterally injected horseradish peroxidase. The commissural projections arise mainly from pyramidal cells in the medial, dorsomedial, and dorsal cortices (medial subfield). Additionally some non-pyramidal neurons in the medial and dorsal cortices contribute to the commissural system. Medial cortex neurons project to the contralateral anterior septum through the anterior pallial commissure. The dorsomedial cortex projects contralaterally via the anterior pallial commissure to the dorsolateral septum and to the medial, dorsomedial, and dorsal cortices. The projection to the medial cortex terminates in two bands at the inner and outer border, respectively, of the cell layer; the projection to the dorsomedial and dorsal cortex ends in a zone in layer 1 which previously has been described to be Timm-negative, and in a diffuse band in the inner half of layer 3. The medial subfield of the dorsal cortex projects through the anterior pallial commissure to the dorsomedial and dorsal cortices with a similar pattern of termination to that found for the dorsomedial cortex. The posterior pallial commissure contains only the projections from the ventral cortex to its contralateral counterpart and to the ventral part of the caudal medial cortex. The similarities found between this commissural system and the mammalian hippocampal interhemispheric connections are discussed.

Notes: The distribution of structural and secretory glycoconjugates in the gastric region of metamorphosing Xenopus laevis was studied by the avidin-biotinperoxidase (ABC) histochemical staining method using seven lectins (concanavalin A, Con A; Dolichos biflorus agglutinin, DBA; peanut agglutinin, PNA; Ricinus communis agglutinin I, RCA-I; soybean agglutinin, SBA; Ulex europeus agglutinin I, UEA-I; and wheat germ agglutinin, WGA). Throughout the larval period to stage 60, the epithelium consisting of surface cells and gland cells was stained in various patterns with all lectins examined, whereas the thin layer of connective tissue was positive only for RCA.-I. At the beginning of metamorphic climax, the connective tissue became stained with Con A, SBA, and WGA, and its staining pattern varied with different lectins. The region just beneath the surface cells was strongly stained only with RCA-I. With the progression of development, both the epithelium and the connective tissue gradually changed their staining patterns. The surface cells, the gland cells, and the connective tissue conspicuously changed their staining patterns, respectively, for Con A and WGA; for Con A, PNA, RCA-I, SBA, and WGA; and for Con A, RCA -I, and WGA. At the completion of metamorphosis (stage 66), mucous neck cells became clearly idpntifiable in the epithelium, and their cytoplasm was strongly stained with DBA, PNA, RCA-I, and SBA. These results indicate that lectin histochemistry can provide good criteria for distinguishing among three epithelial cell types, namely, surface cells, gland cells, and mucous neck cells, and between adult and larval cells of each type.

Notes: Ultrastructural features of the ovotestes, spermatogenesis, and the mature sperm are described for three galeommatid bivalves, Divariscintilla yoyo, Divariscintilla troglodytes, and Scintilla sp., from stomatopod burrows in eastern Florida. All three species yielded similar results except with respect to mature sperm dimensions. The ovotestis contains three types of somatic cells within the testicular portion: flattened myoepithelial cells defining the outer acinal wall; underlying pleomorphic follicle cells containing abundant glycogen deposits; and scattered, amoeboid cells containing lysosomal-like inclusions which are closely associated with developing sperm. Early spermatogenesis is typical of that reported from other bivalves. In contrast, the late stages of spermiogenesis involve the migration and gradual rotation of the acrosomal vesicle, resulting in a mature acrosome tilted about 70° from the long axis of the cell. The mature sperm possesses an elongated, slightly curved nucleus; a subterminal, concave acrosome with a nipple-like central projection; five spherical mitochondria and two centnoles in the middlepiece; and a long flagellum. The rotational asymmetry and the presence of perimitochondrial glycogen deposits in these sperm are unusual in the Bivalvia and may be associated with fertilization specializations and larval brooding common among galeommatoideans.

Notes: Polychaetes normally possess one pair of nuchal organs at the posterior edge of the prostomium or peristomium. They have been regarded as chemosensory organs. The nuchal organs of four marine polychaete species with different habits were investigated by electron microscopy.Although the shapes of nuchal organs can vary greatly from simple ciliary bands (Scolelepis squamata, Spionidae) to retractile tongue-like, piston- or finger-shaped forms (Eteone longa, Anaitides mucosa, Phyllodocidae; Heteromastus filiformis, Capitellidae), the structural components, including the ciliated supporting cells, sensory cells, and nuchal epidermal cells, are essentially similar. The differences basically concern 1) the position of the sensory cells with relation to the ciliated supporting cells, 2) the location and structure of the nuchal nerve, and 3) the structure of the nuchal cuticle.The diverging nature of this modified cuticle is described and discussed in detail. Comparisons are made with the fine structure of nuchal organs of other polychaete species. Similarities of cellular components of nuchal organs are found not only in the four species studied here but also in all nuchal organs investigated so far. This is hypothesized to be due to the fact that the polychaete stem species already possessed nuchal organs with the respective cell types. Differences in the number and distribution of cellular components and in the overall shape of nuchal organs are thought to have evolved in correlation with the equipment of other cephalic appendages and with different habits and modes of nutrition.

Notes: The buccal glands of adults of the Southern Hemisphere lamprey Geotria australis consist of a pair of small, bean-shaped, hollow sacs, embedded within the basilaris muscle in the region below the eyes and to either side of the piston cartilage. Each gland, which is lined by a simple columnar epithelium and surrounded by an incomplete layer of skeletal muscle, discharges its contents into the oral cavity via a long, narrow duct. In downstream migrating young adults, the epithelial cells are low columnar, intermediate in electron density, and contain dark-staining inclusions and numerous lipid-like droplets. After saltwater acclimation, the epithelial cells become taller and the numbers of dark-staining inclusions increase whereas those of lipid-like droplets decline. By the end of the marine phase, the epithelium is more folded and now also contains dark and light cells. The ultrastructure of the epithelium shows the characteristics of both apocrine and merocrine secretion. Although intra-epithelial nerve endings were not observed, axons and occasional neurons are present in the lamina propria. Since the skeletal muscle capsule is also well innervated and contains neurons, a local feed-back mechanism may regulate the release of buccal gland fluid by monitoring the luminal pressure. Contractions of the skeletal muscle capsule and movements of the basilaris muscle during feeding would presumably assist the movement of secretion along the duct. The secretion possesses anticoagulating and haemolytic properties.

Notes: The early development of Pedetontus unimaculatus from maturation to germ rudiment formation has been described by light and electron microscopy. Newly laid eggs of P. unimaculatus are in the metaphase of the first maturation division, and two successive maturation divisions produce two polar bodies. Nuclear divisions up to the eighth or ninth are accompanied by cytoplasmic divisions, and are holoblastic. Each resulting blastomere contains a single nucleus. Most cleavages are radial, but a few are tangential resulting in the formation of primary yolk nuclei. After the eighth or ninth nuclear division, cytoplasmic divisions are restricted to the egg periphery, and these later cleavages are superficial. Boundaries of blastomeres gradually disappear. Nuclei, which settle in the peripheral cytoplasm, proliferate and differentiate into blastoderm cells, and they also give rise to secondary yolk nuclei. A posterior circular region of blastoderm thickens and concentrates to form a germ rudiment 50-100 μm in diameter. During the formation of a germ rudiment the serosal cuticle begins to form.A similar pattern of cleavage was observed in other species of the Machilidae belonging to four genera in two subfamilies (Machilinae, genus Haslundichilis; Petrobiinae, genera Pedetontus, Pedetontinus, Petrobiellus). The cleavage pattern of the machilids closely resembles that found in the myriapod groups, the Symphyla, Diplopoda, ana Pauropoda, as well as in the apterygote Collembola, but it differs from the purely superficial cleavage pattern characteristic of the apterygote Thysanura sensu stricto (Zygentoma) and the Pterygota.It is concluded 1) that the pattern of early total cleavage changing later to superficial cleavage is a plesiomorphic character for the Antennata, and 2) that the purely superficial pattern is an apomorphic character within the Hexapoda.

Notes: The digestive gland (midgut gland, hepatopancreas) of the American lobster, Homarus americanus (Decapoda: Nephropidae), is permeated with terminal arterioles of the hepatic artery. Fixed phagocytes associated with the terminal hepatic arterioles removed two types of non-biogenic, foreign particles (carbon particles and latex beads) that were injected into the blood. These cells play an important role in the cell-mediated immunity of lobsters.

Notes: The digestive gland (midgut gland, hepatopancreas) of the American lobster, Homarus americanus (Decapoda: Nephropidae), is supplied with blood by the hepatic artery. Numerous branches, ending in terminal hepatic arterioles, permeate the organ and discharge blood into the hemal sinuses. Histological and ultrastructural studies show the arterioles to be elongate tubes that lie in the hemal spaces, interspersed among the digestive tubules of the digestive gland. The terminal hepatic arterioles comprise three distinct populations of cells: endothelial cells form the wall of the blood vessel; hemocytes circulate through the lumen of the vessel; and fixed phagocytes are attached to the outer surface of the endothelium. In addition, extracellular membranes form an endothelial intima that lines the lumen and a perforated membrane that covers the outer surface of the arteriole.

Notes: mAb WE3 recognizes an antigen that is developmentally regulated in the wound epithelium of regenerating newt limbs. The antigen is precociously expressed when pieces of WE3-negative wound epithelium axe grafted subcutaneously (Tassava et al.: Recent Trends in Regeneration Research. New York: Plenum Publishing Co., pp. 37-49, 1989). In the present study, we investigated whether the WE3 antigen is expressed in epidermis of subcutaneous grafts of skin. Small pieces of limb skin were grafted into small tunnels in the lower jaw, limb, and tail, oriented either the same as (epidermis facing out) or opposite to (epidermis facing in) the orientation of the host skin. In most cases, the epithelium migrated from the graft along the wounded surface of the tunnel, closed onto itself, and formed a multilayered “emigrant” epithelium. Infrequently, the migrating epithelium combined with the wound epithelium of the insertion wound. In no case did the epithelium migrate over the cut edge of the grafted dermis. Reactivity to mAb WE3 was first seen at 4 days after grafting, when the migrating epithelium had almost closed over onto itself. By 6 days and thereafter, the entire emigrant epithelium was reactive to mAb WE3. While initially restricted to the emigrant epithelium, at 10 days after grafting and thereafter, reactivity was also seen in the epidermis that remained in contact with the dermis. Expression of the WE3 antigen was not influenced by the orientation of the graft nor by the graft site. The results show that, compared to amputated limbs, the epithelium originating from these grafts precociously expresses the WE3 antigen. Also, epidermis of grafted skin is capable of expressing the WE3 antigen.

Notes: Endocrine cells and brush cells at the bronchiolo-alveolar junctions of the lung of neonatal hamsters were studied by transmission electron microscopy. On both sides of the junctions (bronchiolar and alveolar), clusters of endocrine cells occur as neuroepithelial bodies (NEB). A few solitary endocrine cells are also present at the alveolar sides of the junctions. Some endocrine cells reach from the basement membrane to the air space but the area of apical cell membrane exposed to the airway is small as the cells are largely covered by Clara cells in the bronchioles and by thin attenuations of alveolar type 1 cells in the alveoli. Some Clara cells around NEB contain cytoplasmic lamellar bodies, similar to those characteristically associated with alveolar type 2 cells. A few brush cells are also seen at both sides of the junctions. Long wide microvilli with filamentous cores extend from the apices of the brush cells. Endoplasmic reticulum and Golgi apparatus are moderately developed. Well-developed bundles of intermediate filaments course throughout the cytoplasm of some of the brush cells. The functions of endocrine cells and brush cells are unknown. However, the presence of these cells at the bronchiolo-alveolar junctions of neonatal hamster lungs suggests a role in regulation of respiratory function.

Notes: Anolis carolinensis has two aggressive displays involving movements of the hyoid apparatus: erection of the throat and extension of the dewlap. Erection of the throat is an enlargement of the gular region and dewlap extension consists of a vertical erection of the gular flap. Cinefluoroscopy and high speed cinematography show that the dewlap is extended in three phases: 1) protraction of the entire hyoid apparatus; 2) forward pivoting movement of the ceratobranchials II; and 3) retraction of the ceratobranchials II and the entire hyoid apparatus. The cartilaginous elements of the hyoid apparatus are variably mineralized. The entoglossal process and the hypohyals are the most calcified elements. The mineralized portion of the hyoid body, to which the other elements articulate, presents a complex pattern. The calcification of entoglossal process and the hypohyals stop just where they are fused with the hyoid body. The hyoid body presents four mineralized masses, two central corresponding to the base of the ceratobranchials II and two lateral being the head of the ossified ceratobranchials I. The lateral masses articulate on the central masses by a synovial joint. Morphologically, the ceratobranchials II form the hyoid body and become separated at the mid length of the synovial articulation of the ceratobranchials I and the hyoid body. The calcified matrix of the ceratobranchials II gradually changes from a large calcified mass (within the hyoid body) to a semicircle, opened ventrally, which permits their bending during dewlap extension. The highly mineralized posterior tip of the entoglossal process and the hyoid body serve as a pivot to pivoting forward movement of the ceratobranchials II producing at the change of the pattern of mineralization. Forward movement of the ceratobranchials II is produced by electrical stimulation of the M. branchio hyoideus. The opposition of the throat skin to the movement of the ceratobranchials II produces the bending of those longest elements. Electrical stimulation of the hyoid muscles confirms the key role of M. branchiohyoideus during dewlap extension. Simultaneous contractions of all the hyoid and extrinsic tongue (retractor and protractor) muscles with the M. branchiohyoideus during dewlap extension may be a possible motor pattern for dewlap extension in Anolis lizards.

Notes: The ovotestis of Arion hortensis was investigated by electron microscopy, using serial ultrathin sections and freeze-fracture. Desmosome-like junctions between Sertoli-Sertoli and Sertoli-germ cells (spermatogonia, spermatocytes, spermatids, and spermatids just prior to spermiation) were studied. Desmosome-like junctions were circular when viewed en face and 90--180 nm in diameter. The intercellular space at the junctional site was 15-25 nm in width. An intermediate dense line was absent.Freeze-fracture replicas showed that these junctions formed groups, with one to ten junctions within each group. Groups of junctions were scattered over the Sertoli cell surface. The most prominent feature of this junction was an electron-dense plaque on the cytoplasmic face of the plasmalemma. We describe variation in the development of the electron-dense plaque on the germ cell side at different stages in the development of the germ cell. In the spermatogonium and spermatocyte stages, desmosome-like junctions had equally developed electron-dense plaques. The plaques are pronounced in junctions between Sertoli cells and spermatocytes/spermatids and less developed in relation to late spermatids where nuclear condensation is complete, and appear to be lost at spermiation. Finger-like processes arise from the Sertoli cell as desmosome-like junctions are lost at spermiation.Hypertonic fixative solutions containing dextrose were applied to the ovotestis resulting in cell shrinkage. The intercellular space between Sertoli cells and germ cells was increased except where the desmosome-like junctions were present. We suggest that desmosome-like junctions provide strong adhesive sites between Sertoli and germ cells.

Notes: The ultrastructural studies have shown three types of motor endings in the macaque intrafusal fibers: (1) unindented axon terminals with smooth or shallowly folded postsynaptic membrane; (2) indented terminals with few postsynaptic folds; and (3) indented terminals with heavily folded postsynaptic membrane. The terminals on bag 1 and chain fibers were generally more indented than those on the bag 2 fibers. Deeply indented terminals with highly folded postsynaptic membranes were noticed on the bag 1 and chain endings in spindles from lumbrical but not the biceps muscle. In the individual intrafusal fibers from the biceps and lumbrical spindles, the degree of indentation did not correlate with the extent of postsynaptic folding (P〉.01). Endings on bag 1 and chain fibers in the lumbrical spindles showed a positive correlation between indentation of terminals and their distance from the primary sensory endings (P〈.01), whereas the lumbrical bag 2 endings and the biceps intrafusal endings did not (P〉.01). The shape of the intrafusal motor endings thus is independent of their location but dependent on the type of intrafusal fibers.

Notes: Sockeye salmon were transferred rapidly from freshwater to seawater and the changes in gill morphology, in particular the distribution and sizes of chloride and mucous cells on the afferent filamental surface examined. Salmon that successfully adapted to seawater were compared with salmon that did not adapt to seawater and died as a consequence of osmoregulatory failure. The number of mucus cells (density), determined from scanning electron microscopy, increased significantly after seawater challenge. A greater increase in mucus cell density occurred in the salmon that failed to adapt to seawater. Light microscopy of transverse sections of gills detected no difference in mucus cell numbers after seawater challenge. It is proposed that mucus cells that lie just beneath the gill epithelium are activated in response to the seawater challenge, and migrate and open onto the epithelium. Freshwater-adapted salmon that had low densities of chloride cells prior to the seawater challenge failed to adapt, whereas salmon that had high densities of chloride cells adapted successfully to seawater. In the latter, the density of chloride cells on the afferent surface decreased after 30 days in seawater. The apical surface of the chloride cells of freshwater-adapted sockeye were either smooth or covered with microvilli. A greater proportion of microvilli-covered chloride cells occurred in the freshwater-adapted salmon that subsequently adapted to seawater.

Notes: The ultrastructure of scalariform junctions in the Malpighian tubules of the hemipteran Rhodnius prolixus and the dipteran Aedes taeniorhynchus is described. Both autocellular and intercellular scalariform junctions are illustrated. This is the first report of scalariform junctions in the Malpighian tubules of a dipteran. When combined with previous observations by other authors, the presence of scalariform junctions has now been reported in the Malpighian tubules of insects from five orders, including ametabolous, hemimetabolous, and holometabolous forms. The cell types in which scalariform junctions were found in R. prolixus and A. taeniorhynchus differ in the direction of ion and fluid transport. The cells share the capacity to transport KCl. These same cells also possess morphological features promoting close associations of mitochondria and plasma membranes in the apical region of the cell. The possible role of scalariform junctions is discussed in light of these observations.

Notes: The morphology, cell types, and innervation of the several small papillae (x̄ = 17) and two larger papillae, which together form a ring just outside the fimbriae surrounding the suctorial disc of adult Geotria australis, have been studied using various histological stains, including silver impregnation, and scanning and transmission electron microscopy. The epithelium of all papillae consists almost entirely of mucigenic cells. The multivillous and oligovillous cells, which are found elsewhere in the lamprey epidermis, were not observed, and Merkel and polyvillous cells are rare. Free nerve endings are common, however, in the basal layers of the epidermis. Unlike the small papillae, the two large papillae contain a core of skeletal muscle and a prominent layer of dermal collagen. In the submucosa of these large papillae, the nerves form a dense, compact layer that contains many large and probably sensory axons. It is suggested that the oral disc papillae of adult G. australis are encapsulated mechanosensory structures that play a role in enabling the animal to locate and attach to a suitable point on host fishes or other surfaces.

Notes: Although torsion (axial twisting) is rare in living structures, some starfish routinely use ray torsion in the righting process. This study examined the torsional properties of the ray and dorsal body wall of Echinaster spinulosus (Echinodermata: Asteroida: Spinulosidae). The body wall of the ray is composed of a reticular skeleton composed of CaCO3 ossicles sandwiched between collagenous layers in which the fibers are orthogonally oriented. G, the shear modulus of the dorsal body wall, determined from a torsion pendulum, was 95.3 MPa, and damping was extremely pronounced (Δ = 1.36). The torque-rotation curve was J-shaped, and G determined from this data was 176 MPa. Torsional stress relaxation was rapid, with the relaxation spectrum skewed to the left and τmax = 2.3 for anaesthetized tissue and 2.7 for unanaesthetized tissue.Analysis of ray geometry showed that the ambulacral groove reduced torsional stiffness by about two orders of magnitude compared to an ungrooved ray. Ray taper reduced the stiffness of the tip relative to the root. The shear stress distribution determined for the ray cross-section showed stress concentrations around the ambulacral arch, the outer body wall surface, and the inner body wall surface. The ossicles are situated to minimize torsional stiffness of the ray.

Notes: Methyl methacrylate vascular corrosion replicas were used to examine the macrocirculation in the head region and the microcirculation of respiratory vessels in the air-breathing swamp eel Monopterus cuchia. Fixed respiratory tissue was also examined by SEM to verify capillary orientation. The respiratory and systemic circulations are only partially separated, presumably resulting in supply of mixed oxygenated and venous blood to the tissues. A long ventral aorta gives rise directly to the coronary and hypobranchial arteries. Two large shunt vessels connect the ventral aorta to the dorsal aorta, whereas the remaining ventral aortic flow goes to the respiratory islets and gills. Only two pairs of vestigial gill arches remain, equivalent to the second and third arches, yet five pairs of aortic arches were identified. Most aortic arches supply the respiratory islets. Respiratory islet capillaries are tightly coiled spirals with only a fraction of their total length in contact with the respiratory epithelium. Valve-like endothelial cells delimit the capillary spirals and are unlike endothelial cells in other vertebrates. The gills are highly modified in that the lamellae are reduced to a single-channel capillary with a characteristic three-dimensional zig-zag pathway. There are no arterio-arterial lamellar shunts, although the afferent branchial artery supplying the gill arches also supplies respiratory islets distally. A modified interlamellar filamental vasculature is present in gill tissue but absent or greatly reduced in the respiratory islets. The macro- and micro-circulatory systems of M. cuchia have been considerably modified presumably to accommodate aerial respiration. Some of these modifications involve retention of primitive vessel types, whereas others, especially in the microcirculation, incorporate new architectural designs some of whose functions are not readily apparent.

Notes: Transmission electron microscopy reveals that the spermatocytes of the hookworm Ancylostoma caninum contain an abundance of Golgi complexes, ribosomes, specialized membranous organelles, and long strands of smooth endoplasmic reticulum. These organelles remain abundant until the early spermatid stage of sperm development, when they reach their maximum abundance and maturity and the production of new ones ceases. Golgi complexes, ribosomes, and excess SER, which are not functional after this stage, become segregated and confined to the posterior portion of the spermatid in a polar lobe. Later, the polar lobe together with excess cytoplasmic matrix is bound by a membrane and dissociated from the spermatid as a residual body. The spermatid is then devoid of Golgi complexes and ribosomes. Formation of residual bodies as sperm cells mature may be considered a type of cell excretion.

Notes: The development of the morphologic features of neurons in the anterior dorsal ventricular ridge (ADVR) has been followed in Golgi preparations from the lizard Gallotia galloti between embryonic stage 32 and post-eclosion stages of specimens 3.6-4.5 cm in length. The differentiation sequence of multipolar and bitufted neurons was established. Dendritic growth cones are present after stage 34. Filiform dendritic processes are replaced later on by spines. Clusters of neurons first appear at stage 39 in the periventricular zone, the cells becoming Golgi-impregnated in pairs. After hatching, the number of impregnated cells per cluster increases.

Notes: Six different lectins were used to study the carbohydrate nature of the hyaline layer (HL), the external extracellular matrix of the starfish embryo. Thin sections of embryos fixed in the late gastrula stage were incubated with five fluoresceinated lectins: Con A, WGA, RCA, UEA-I, and SBA. All but UEA-I labelled the HL, suggesting that the following sugars are present: mannose and/or glucose, glcNAc and/or Neu5Ac, galactose, and galNAc. The different lectins produced variable degrees of labelling, with WGA, RCA, and SBA producing more intense labelling than Con A. Binding of lectins by the HL was studied at the ultrastructural level by exposing ultrathin sections to the following lectin-gold conjugates: Con A, WGA, PNA, SBA, and LFA. Lectin binding was observed over the various regions of the HL, recognized by Crawford and Abed (J. Morphol. 176:235-246, '86), i.e., the intervillus layer, the supporting layer and the coarse outer meshwork. Local differences in labelling patterns were observed among the various lectins, with SBA labelling all regions intensely, WGA and PNA labelling the supporting layer predominantly, and Con A labelling the HL only lightly. No labelling was observed with LFA. These lectin-labelling patterns in the HL demonstrate the presence of different glycoconjugates in different regions of the HL, suggesting that the layers differ biochemically. The existence of biochemical differences strengthens the idea that each layer may have different functions in the developing starfish embryo.

Notes: The diversity in cranial morphology of living geomyoids, including pocket gophers (Thomomys), spiny pocket mice (Heteromys and Liomys), desert pocket mice (Chaetodipus and Perognathus), and kangaroo rats and mice (Dipodomys and Microdipodops) is accompanied by only a few differences in their cephalic arterial circulation. The principal difference is the origin of the pterygopalatine artery, which serves the orbit and rostrum. In dipodomyines and perognathines it originates as a stapedial branch of the internal carotid artery and passes through the middle ear en route to the braincase. In geomyines and heteromyines it originates as an internal maxillary branch of the external carotid artery and enters the braincase directly. Either geomyines and heteromyines are convergent in this respect, or the currently recognized family Heteromyidae is paraphyletic. The stapedial artery is the same size in early embryos of T. bottae and D. merriami, but in the former species it fails to grow and disappears in juveniles. Comparison of developmental series of D. merriami and T. bottae revealed that the decline of the artery in the latter species is preceded by a greater degree of arterial coarctation, or narrowing, as it passes though the developing stapes. The loss of the stapedial artery is correlated with an enlarged masseter profundus muscle in T. bottae and with an unusually small stapes in T. bottae, H. desmarestianus, and L. salvini. I hypothesize that the primitive condition for geomyoids is the presence of both stapedial and internal maxillary arteries, that the stapedial artery was lost in geomyines and heteromyines because of the constraint on its size posed by the stapes, and that the stapedial artery was retained in dipodomyines because enlargement of the stapes accompanied bullar inflation in these taxa and lifted the constraint on the size of the stapedial artery.

Notes: Reconstructions from serial sections reveal that the digestive system consists of a pharynx esophagus, crop, midgut, and rectum. Two main stems from the branched enteral diverticula are connected to the lateral regions of the crop by right rind left arms. Glandular tissue surrounds the enteral diverticula proximally. A strong sphincter separates the crop and midgut, whereas the midgut and rectum are separated by a weak sphincter. Cuboidal epithelium lines the pharynx, esophagus, crop, and rectum, whereas cuboidal and club-shaped epithelia line the midgut. The cuboidal cells possess elongated nuclei and numerous vacuoles, suggesting that absorption takes place in the midgut.

Notes: The movement of the entire tongue and intermolar eminence during mastication is described in the domestic rabbit (Oryctolagus cuniculus). Tongue movement and jaw position were analyzed videofiuorographically from separate lateral and dorso-ventral views in six rabbits. Metallic markers were inserted into the tongue so that its movement was visible on the fluorographic image. Frame-by-frame analysis of the videofluorographic tape recordings demonstrates that tongue movement in all animals was identical in direction during each part of the chewing cycle. In the lateral view the forepart of the tongue moves down and forward during the opening stroke, whereas the intermolar eminence moves up and forward to appose the palate. During the closing stroke, as the tip of the tongue moves up and back, the intermolar eminence lowers from the palate and retracts. During the power stroke the forepart of the tongue is at its most elevated and retruded position, while the intermolar eminence is its lowest and most retruded. The dorso-ventral view showed that lateral movement of the tongue and mandible are highly synchronous. The intermolar eminence decreases in width during the power stroke, possibly twisting to place or keep food on the teeth. An anterior to posterior undulating movement of the entire tongue occurs throughout the chewing cycle. As the intermolar eminence elevates to appose the palate during the opening stroke, it may replace the bolus on the teeth on the chewing side. The intermolar eminence also appears to be twisting during the closing and power strokes to place or maintain food on the teeth.

Notes: The structure of the nephron in the ranid frog, Rana cancrivora, was studied by light and electron microscopy. This frog is the only amphibian species to live in mangrove swamps of very high salinity. The nephron consists of the following parts: renal corpuscle, ciliated neck segment, proximal tubule, ciliated intermediate segment, distal tubule, connecting tubule, and collecting duct. The distal tubule is located in the ventromedial region of the kidney, and the other tubules are situated in the dorsolateral region. Renal corpuscles are found between the two regions. Some renal corpuscles have a wide Bowman's space because of the small glomerulus within them. The proximal tubules are composed of columnar cells with a dense luminal brush border of long microvilli and numerous apical vesicles and vacuoles. The initial part of the distal tubule consists of heavily interdigitated cells, characterized by a very regular palisade arrangement of mitochondria. In the terminal part of the distal tubule, shorter mitochondria of the infolding cells are situated irregularly around the nucleus. The connecting tubule consists of principal cells and canaliculus cells. The collecting duct consists of columnar or cuboidal cells; cytoplasmic organelles are relatively sparse. The canaliculus cells are intercalated between principal cells from the terminal distal tubule to the proximal part of the collecting duct. Our findings indicate that the kidney of R. cancrivora is structurally similar to kidneys of other amphibians. These findings are discussed with regard to probable correlations between ultrastructure and function in R. cancrivora.

Notes: This light and transmission electron microscopical study shows that the first polar body is given off before ovulation and that part of its cell membrane and that of the surrounding oocyte have long microvilli at the time of its ejection. Several layers of cumulus cells initially surround the secondary oocyte and first polar body, but the ovulated oocytes in the oviducts in the process of being fertilized do not have cumulus cells around them. Partly expelled second polar bodies occur in the oviduct; they are elongated structures that lack organelles and have electron-dense nuclei. A small fertilization cone appears to form around the sperm tail at the time of sperm entry into the egg and an incorporation cone develops around the sperm head in the egg cytoplasm. In three fertilized eggs a small hole was seen in the zona, which was presumably formed by the spermatozoon during penetration. Cortical granules, present in ovarian oocytes, are not seen in fertilized tubal or uterine eggs; release of their contents probably reduces the chances of polyspermy, although at least one polyspermic fertilized egg was seen and several other fertilized eggs had spermatozoa within the zona pellucida. In the zygote the pronuclei come to lie close together, but there was no evidence of fusion. A “yolk mass,” which becomes eccentric before ovulation, is extruded by the time the two-cell embryos are formed, but many vacuoles remain in the non-yolky pole of the egg. A shell membrane of variable thickness is present around all uterine eggs but its origin remains undetermined.

Notes: The morphology and anatomical relationship of the paraphysis, anterior choroid plexus, and endolymphatic tubules of Hyla versicolor suggest that these structures may act as a functional unit to regulate composition of the cerebrospinal fluid (CSF). Ependymal cells of both the paraphysis and the choroid plexus exhibit ultrastructural features (an extensive microvillar border, large intercellular spaces containing an amorphous material, and apically located mitochondria) which indicate active exchange between the blood and CSF. Mast cells (which may play a role in regulating vascular permeability) also occur on the brush border. The tubules of the endolymphatic sacs were found to lie in close relation with the dorsal portion of the paraphysis. The endolymphatic organ is known to play a role in systemic buffering during respiratory acidosis and may influence Na/K fluxes via calcium release. The association of the paraphysis with the endolymphatic tubules may therefore represent an important mechanism for ion regulation in the CSF of amphibians. The ultrastructure of the pineal organ agrees with descriptions for other species. No pineal stalk was present. Photoreceptor inner and outer segments project into a central lumen continuous with the third ventricle. Outer segments show signs of disorganization. Photoreceptor/neural dendrite contacts involve synaptic ribbons and conventional synapses.

Notes: Asellus aquaticus is a freshwater isopod with an unusually long excretory duct of the maxillary gland. The ultrastructure of this gland is described in detail for the first time. Only one comparable description of an isopod excretory gland has been published until now (for a marine species). The gland is composed of an end sac (coelomosac) with podocytes which allow passive ultrafiltration by haemolymph pressure. The podocytes resorb material (probably proteins) from the primary urine. The opening to the excretory duct is controlled by a valve, which consists of muscular sphincter cells and larger valve cells; the latter protrude into the duct. The ultrastructure of cells in different regions of the excretory duct and of the terminal duct is described and correlated with the possible function of the organ.

Notes: Using Golgi techniques we have studied neuronal cell types in the anterior dorsal ventricular ridge (ADVR) of the adult lizard Gallotia galloti. Multipolar, bitufted, and juxtaependymal neuronal forms were found. The multipolar and bitufted neurons are present in both the periventricular and central ADVR zones. Multipolar neurons can be subdivided into multipolar neurons with polygonal somata and four to six main dendritic trunks and multipolar neurons with pyramidal somata and three or more dendritic trunks. The former are the cells most frequently impregnated in the ADVR. In the population of bitufted neurons, we distinguish subtypes I, II, and III according to the number of dendritic trunks that emerge from the somata. Juxtaependymal neurons are restricted to a cell-poor zone, adjacent to ependymal cells. Their dendrites either are orientated parallel to the ventricular surface or extend into the periventricular zone. The dendrites of ADVR neurons have pedunculated spines with knob-like tips. However, such spines do not appear on the somata or on the primary dendritic trunks. The number of spines is scarce or moderate. The periventricular neuronal clusters contain two to five cells. The morphology of these neurons is mainly multipolar, but we also found some bitufted neurons.

Notes: The binding of seven lectins (concanavalin A, Con A; Dolichos biflorus agglutinin, DBA; peanut agglutinin, PNA; Ricinus communis agglutinin I, RCA-I; soybean agglutinin, SBA; Ulex europeus agglutinin, UEA-I; and wheat germ agglutinin, WGA) to the small intestine in metamorphosing Xenopus laevis was studied by the avidin-biotin-peroxidase (ABC) method. The staining pattern of the epithelium with all lectins except for UEA-I and Con A changed gradually during metamorphic climax; the main component of the epithelium, absorptive cells, gradually became positive for DBA, PNA, and SBA and the scattered goblet cells for RCA-I and WGA. On the other hand, the change of the staining pattern in the connective tissue occurred only for Con A, RCA-I, and WGA, and this change took place rapidly at the beginning of climax (stage 60). Increased staining for Con A and WGA at stage 60 was observed only in a group of connective tissue cells close to the epithelium and in the basement membrane. As metamorphosis progressed, this localization of the staining intensity became less clear. At the completion of metamorphosis (stage 66), the absorptive cells were stained with all lectins except for UEA-I, whereas the goblet cells stained only with RCA-I and WGA. These results indicate that lectin histochemistry can distinguish between larval and adult cells of both two epithelial types (absorptive and goblet cells). The technique may also identify a group of connective tissue cells, close to the epithelium, that possibly induce the metamorphic epithelial changes.

Notes: Comparison of mesopodial skeletal patterns found in native and regenerated limbs of the salamander Plethodon cinereus reveals variant patterns unique to each group. Variant patterns in native limbs are based on fusions between laterally adjacent elements (i.e., in the anteroposterior axis). Variant patterns in the mesopodia of regenerated limbs usually exhibit fusions among proximodistally adjacent elements. Analysis of regenerates derived from limb amputation at different levels shows that the axis of fusion between regenerated mesopodial elements remains the same (i.e., proximodistal) independent of amputation level. However, the frequency of specific fusion combinations is unexpectedly sensitive to amputation level. Proximal (stylopodial) amputation results in mesopodial patterns with predominantly preaxial fusion combinations; distal amputation produces mesopodial patterns with predominantly postaxial fusion combinations. This finding is discussed in the context of other recent studies in which amputation level influenced limb regeneration patterning.

Notes: In a Golgi study of the area triangularis (AT), a rostral nucleus of the ventral thalamus of Gallotia galloti, we have identified four major neuronal types on the basis of their morphological characteristics: medium-sized fusiforms with two processes, medium-sized fusiforms with three or four processes, small bipolars, and small and medium-sized multipolars. These neurons are characterized by a simple morphology and radial arrangement. Cell size varies from small to medium, and all axons project laterally. These characteristics distinguish AT neurons from those of neighboring nuclei. In addition, we found some evidence of differential topographic distribution of each neuronal type within the nucleus. Medium-sized fusiform neurons with two processes are located in the most ventral part, where they constitute the ventral nuclear limit. Small multipolar neurons prevail in the dorsal and ventromedial parts, and in the rest of the nucleus medium-sized neurons, including both fusiform with three or four processes and multipolar types, are normally found. Finally, we discuss a putative homology of the reptilian AT with a part of the mammalian zona incerta.

Notes: The mouth apparatus in Branchiobdella pentodonta was studied by electron microscopy. The opening is situated dorsal to the adhesive disk of the anterior sucker and is surrounded by a ring of 16 papillae. The papillae have mono-layered epithelium, muscle fibers, glandular processes, and taste and olfactory organs like “sensitive buttons.” The oral cavity contains jaws with horny teeth and “sensitive buttons,” and is surrounded by a ring of circular muscle fibers that connect to the muscle fiber of the papillae. This apparatus shows some analogies to that of Hirudinea, such as the presence of sucker and jaws with horny teeth.

Notes: The Harderian gland blood supply of female and male hamsters was studied using light and electron microscopy. A profuse vascularization surrounding secretory acini was observed. Among the blood vessels, the existence of large and irregular sinusoidal capillaries was apparent. These sinusoids appeared in close association to the basal aspect of the secretory cells. Typical, small, fenestrated capillaries were also observed within the connective tissue. The existence of this particular vascularization together with other morphological features of the secretory cell basal pole suggest a possible endocrine function of these orbital glands.

Notes: The process of spermiation in the ratfish Hydrolagus colliei is described and compared with that in mammals and amphibians. Spermiation in this species involves prior fluid space expansion both within the apical parts of the Sertoli cytoplasm and in the spaces between Sertoli cells and spermatids. The apical ends of Sertoli cells fragment, including the parts immediately around the spermatid acrosomes. Intercellular material between the spermatid tips and the Sertoli cells dissolves. Concurrently an opening from the seminiferous follicle into the efferent ductule is made by means of changes in cell shape and separation of Sertoli cells and efferent ductule cells that adhere to each other up to the time of sperm release.

Notes: The galatheid squat lobster, Munida rugosa, has compound eyes of the reflecting superposition type in which a distal cone cell layer and a proximal rhabdom layer are separated by an extensive clear zone. The eye is shown to have certain unique features. In all other reflecting superposition eyes, the clear zone is traversed by crystalline tracts formed by the cone cells. In M. rugosa a thin distal rhabdom thread, formed by the eighth retinula cell, connects the cones to the proximal fusiform rhabdoms. The cytoplasm of the other retinula cells also crosses the clear zone in a complex pattern. Fully light-adapted ommatidia are optically isolated by limited migrations of distal shielding pigments. A reflecting pigment multilayer lines each cone to facilitate the formation of a superposition image. This also shows a light-induced change which may limit the acceptance angle of the eye during light adaptation.

Notes: The structures of the dermal scales and the cells surrounding the scales in two species of gymnophione amphibians were studied using histochemistry and light, scanning and transmission electron microscopy. Scales are composed of a basal platt of several layers of unmineralized collagenous fibers topped with mineralized squamulae. Squamulae are composed of numerous mineralized globules and mineralized, thick collagen fibers. Mineralization is therefore both spheritic and inotropic. Isolated flattened cells lie on the outer surface of the squamulae and seem to be involved in mineral deposition. Cells that line the basal plate synthesize the collagenous stroma of the plate. Each scale lies in a thin connective tissue pocket, and a large connective tissue pouch includes several scales in each annulus.The similarities of gymnophione scales to elasmoid scales of osteichthyans are largely superficial. Aspects of mineralization and of pocket development differ considerably. There are also similarities, as well as differences, in the gymnophione scales and osteoderms of amphibians and of reptiles. We consider that such dermal structures have arisen many times in diverse lineages of vertebrates, and that these are expressions of properties of dermal collagen to support mineralization by specialized dermal cells. However, we recommend that the term “dermal scale” be used for the mineralized dermal units of osteichthyans and gymnophiones, and “osteoderm” for the dermal structures of frogs and squamates, with the understanding that the terminology recognizes certain convergent attributes of shape and structure, but not of process.

Notes: The innervation pattern of the respiratory gill arches of the carp (Cyprinus carpio) is described. The gill region is innervated by the branchial branches of the glossopharyngeal and vagal nerves. Each branchial nerve divides at the level of or just distal to the epibranchial ganglion into: 1) a pretrematic branch, 2) a dorsal pharyngeal branch, and 3) a posttrematic branch. The dorsal pharyngeal branch innervates the palatal organ in the roof of the buccal cavity. The pretrematic and posttrematic branches innervate the posterior and anterior halves, respectively, of the gill arches bordering a gill slit. Each branch splits into an internal and an external part. The internal bundle innervates the buccal side of the gill arch, including the gill rakers. The external bundle terminates in the gill filaments. The epibranchial motor branch, a small nerve bundle containing only motor fibers, circumvents the ganglion and anastomoses distally with the posttrematic branch. The detailed course and branching patterns of these branches are described.

Notes: In Canis and Ursus the largest proportion of attachments of muscles of the shoulder and brachium on the scapula and humerus is direct; fewer attachments are aponeurotic or tendinous. In both genera most attachments can be associated with superficial osteological features (scars or delimitable surfaces); attachments that lack such features are direct. Most aponeurotic attachments are associated with rugose scarring whereas tendinous attachments are often associated with smooth surfaces. Although most attachments can be associated with osteological features the areal extent of attachment is often not inferrable from the bone. The inference of muscle size or functional significance from osteological features is problematic. The amount of myological information that can be deciphered from the osteology in Canis and Ursus is greater than that reported for particular members of other vertebrate groups which suggests that there may be differences in the degree to which muscles can be reconstructed from superficial osteology alone. Nonetheless, even in mammals such as the Carnivora, detailed muscular reconstructions in extinct taxa cannot be achieved without reference to the musculature of extant relatives. Such reconstructions rely on assumptions, that often have not been adequately tested, regarding the similarity of musculature in closely related taxa. This testing and well corroborated hypotheses of phylogenetic relationship are essential for the evaluation of the accuracy of reconstructions of the musculature in fossil vertebrates.

Notes: When fixed in the presence of alcian blue, extracellular matrix (ECM) in the embryonic asteroid blastocoel can be visualized by light and electron microscopy as a fibrous meshwork encrusted with alcianophilic material. In early to mid-gastrulae, the ECM is associated with the basal laminae underlying the ectoderm and endoderm. It also forms a fibrous meshwork between them in the posterior part of the blastocoel. In early larvae, when mesenchyme cells arrive at the esophagus to differentiate into smooth muscle, very little ECM is associated with the stomach region. In contrast, a meshwork of long ECM strands radiates from the esophageal basal lamina which connects to a dense ECM web associated with the inner aspect of the dorsal ectoderm. This dorsal web is associated, in turn, with numerous long ECM strands which run parallel to the stomodeum. The strands located between the esophagus and the ectoderm appear when the mouth and coeloms form and may be responsible for a constriction of the ectoderm that forms in this region. During late gastrula one population of mesenchyme cells becomes associated with the esophageal region and differentiates into muscle. Most of the other mesenchyme cells stop migrating through the esophageal web at this time. Less alcianophilic material is associated with the esophageal basal lamina, and the ECM adjacent to the esophagus in the late gastrula and early bipinnaria larvae. The arrangement of the ECM elements suggests that they could be involved in controlling the migration of mesenchyme cells, particularly those destined for the esophagus.

Notes: Some unusual specialized structures of the tunic and epidermis in Polyandrocarpa misakiensis were studied histologically, histochemically, and electron microscopically. The tunic is leathery, containing fibers. Dorsal epidermal cells show cytoplasmic bulges at their apical ends, suggesting formation of tunic by the epidermis. Both siphons are characterized by a well-developed velum. In the dorsal mantle, especially around the siphons, numerous elongate cord-like structures of the tunic (10-30 μm in diameter) extend into the hemocoel. Each tunic cord originates from the extra-epidermal tunic, ends distally in a spade-shaped swelling, and is covered by flattened epidermal cells. The tunic cords probably act as connectors between tunic and mantle. Glomerulocytes, a kind of blood cell, are distributed throughout the hemocoel. They are disc-shaped (12-13 μm in diameter, 3 μm thick), and are characterized by a concentric fiber structure in the cytoplasm. The intracellular fibers are similar to the tunic fibers both morphologically and histochemically. The glomerulocytes appear to be derived from epidermal cells; their differentiation occurs in all regions of the epidermis. The function of glomerulocytes is unknown. Small club-shaped bodies which are intensely eosinophilic are distributed here and there in the dorsal epidermis. These eosinophilic bodies are usually located individually in epidermal pockets, and are protruded into the hemocoel. The eosinophilic body is proteinaceous and PAS-positive; it may be a secretory product of the covering epidermis. No physiological role of the eosinophilic body is yet clear. During blasto-genesis, incipient tunic cords, glomerulocytes, and eosinophilic bodies appear almost simultaneously at a stage shortly before the opening of siphons.

Notes: The dewlap is an extendible flap of skin ordinarily folded under the throat. Lizards, particularly those in the genus Anolis, extend their dewlaps during interactions with conspecifics, other lizards, and potential predators. Dewlap extension is effected by movements of elements of the hyoid apparatus. This paper describes the anatomy of the hyoid and associated musculature in Anolis equestris, a large arboreal lizard with a prominent dewlap. A mechanism for dewlap extension is proposed based on results of morphological and experimental techniques.Specializations of the hyoid skeleton for dewlap extension include elongated second ceratobranchials and highly movable joints between the ceratohyals and the hypohyals and between the first ceratobranchials and the body of the hyoid. A well developed M. ceratohyoideus extends between the ceratohyals and the first ceratobranchials of the hyoid apparatus. During dewlap extension, the hyoid apparatus acts as a first order lever. Contraction of M. ceratohyoideus pulls the ceratohyals posterorly causing the hypohyals and the body of the hyoid to rotate dorsally around the first ceratobranchial/body joints. This movement results in the second ceratobranchials swinging forward and down, unfolding the dewlap. The relative immobility of the first ceratobranchials provides stability to the hyoid apparatus during dewlap extension. A comparison is made of dewlap extension and other hyoid displays.

Notes: The spleen of sea bass (Dicentrarchus labrax) is composed mainly of red pulp, whereas the white pulp is poorly developed. The red pulp consists of clear reticular cells intermingled with blood cells, sinusoids, and melanomacrophage centers (MMCs). The MMCs are enclosed by an interrupted connective tissue capsule and show some areas in continuity with the adjacent pulp. The MMCs are formed by the association of free macrophages that have phagocytosed some blood cells. Sparse white pulp is diffuse, forming a cuff around the pulp arteries and MMCs, or occurring in small groups between the splenic cords. A longitudinal artery and vein, lying side by side, extend the length of the spleen. Frequently the capillaries are surrounded by a sheath of macrophages or ellipsoids. These macrophages may contain erythrocytes in varying degrees of degradation. Lymphopoiesis and plasmapoiesis occur in the sparse lymphold areas. Abundant plasma cell groups may indicate the presence of antibody production.

Notes: The behavior of the nuclei of pharyngeal outer epithelial cells was observed by electron microscopy during regeneration of head fragments of planaria transected at the prepharyngeal region. On the fourth day of regeneration, the surface cells of the pharyngeal rudiment show some evidence of differentiation: septate desmosomes and immature rod-shaped bodies. These cells then develop many cilia and a few microvilli on their free surfaces, and the electron-density of their karyoplasm and cytoplasm increases. The basal cytoplasmic processes of the surface cells protrude into the intercellular spaces between underlying cells. Each elongated nucleus goes down into one of these processes. Two types of nuclear descent are observed. The first type occurs when the basal lamina has not yet formed under the epithelial cells. The second type occurs when the basal lamina has already developed under the epithelial cells. Many microtubules are seen running along the long axis of the cells with descending nuclei. Fine fibrous bodies are frequently observed in the descending nuclei of the epithelial cells. Intercellular substances with moderate electron-density are observed sporadically in the spaces between descending cytoplasmic processes and surrounding cells. Glycogen granules accumulate in large numbers in the basal cytoplasm in the vicinity of the descended nucleus. The mechanism of the descent of the perikarya of the pharyngeal outer epithelial cells is discussed in terms of these results.

Notes: Several muscles of the cat hindlimb, including biceps femoris and tenuissimus, are composed of short, in-series muscle fibers with tapered intrafascicular terminations. Tension generation and transmission within such muscles requires that active fibers should be mechanically coupled in series via myomyous junctions, specialized connective tissue attachments, or the endomysium. This report establishes that the tapered fibers of the cat biceps femoris and tenuissimus muscles have insignificant numbers of either myomyous or specialized connective tissue junctions. Tension appears to be transmitted in a distributed manner across the plasmalemma of the tapered (and probably the non-tapered) portions of the fibers to the connective tissue of the endomysium, which is therefore an essential series elastic element in these muscles. Subplasmalemmal dense plaques were identified and may play a role in transmembrane force transmission. In addition to the endomysium, passive muscle fibers may also serve to transmit tension between active fibers, and therefore should also be considered to be series elastic elements.

Notes: The dorsal vessel (DV) in the abdomen of the blood-feeding insect Rhodnius prolixus was divided functionally into two regions, the heart, into which haemolymph entered the DV through four pairs of ostia located in abdominal segment VII, and the aorta, along which the haemolymph was propelled from abdominal segment VI to the thorax. Osmium-fixed whole mounts revealed the DV to consist of spirally arranged striated muscle fibers and to possess two rows of ventrally attached longitudinal fibers extending the length of the abdomen. Seven pairs of alary muscles were found attached to the DV in the posterior abdominal segments. Contractions of the alary muscles attached to the ventral surface of abdominal segments VII and VIII served to expand the heart. Electron microscopy revealed the DV to consist of a thin layer of contractile elements surrounded by an inner (intima) and outer (adventitia) connective tissue layer. Embedded in the intima along each lateral side of the DV were two large groups of endocardial cells extending the length of the DV. A small group of pericardial cells was embedded in the adventitia along the mid-ventral side of the DV, and clusters of pericardial cells were found attached to the alary muscles. Nerve terminals were found only on the heart: they contained agranular synaptic vesicles approximately 30 nm in diameter and densely stained granules approximately 100-120 nm in diameter. These structural components are discussed in relation to the role of the DV in circulation.

Notes: Gills of Chiton olivaceus, a primitive mollusc, are relatively simple in their structure and ultrastructure but are well adapted to a life in the intertidal zone. In contrast to some other molluscs, there is no differentiation of the gill epithelium into functional regions other than respiratory ones. Ciliation of the epithelium in certain areas may optimize water flow from the outer to the inner part of the mantle cavity. The hemolymph sinuses are oriented so that hemolymph flows in the opposite direction. Interstitial cells link epithelial cells with nerve endings. Muscle cells as well as the collagenous matrix in the connective tissue differ within the main gill axis and the lateral lamellae. The life cycle of immunoactive cells within the connective tissue and the hemolymph is described.

Notes: While ontogenetic analyses of skull development have contributed to our understanding of phylogenetic patterns in vertebrates, there are few studies of taxa that undergo a relatively discrete and rapid change in morphology during development (metamorphosis). Morphological changes occurring in the head at metamorphosis in tiger salamanders (Ambystoma tigrinum) were quantified by a morphometric analysis of cranial osteology and myology to document patterns of change during metamorphosis. We employed a cross-sectional analysis using a sample of larvae just prior to metamorphosis and a sample of transformed individuals just after metamorphosis, as well as larvae undergoing metamorphosis. There were no differences in external size of the head among the larval and transformed samples. The hyobranchial apparatus showed many dramatic changes at metamorphosis, including shortening of ceratobranchial 1 and the basibranchial. The subarcualis rectus muscle increased greatly in length at metamorphosis, as did hypobranchial length and internasal distance. A truss analysis of dorsal skull shape showed that at metamorphosis the snout becomes wider, the maxillary and squamosal triangles rotate posteromedially, and the neurocranium shortens (while maintaining its width), resulting in an overall decrease in skull length at metamorphosis.These morphometric differences are interpreted in light of recent data on the functional morphology of feeding in salamanders. Morphological reorganization of the hyobranchial apparatus and shape changes in the skull are related to the acquisition of a novel terrestrial feeding mode (tongue projection) at metamorphosis. Metamorphic changes (both internal and external) that can be used to judge metamorphic condition are discussed.

Notes: We measured the lengths and diameters of four long bones from 118 terrestrial carnivoran species using museum specimens. Though intrafamilial regressions scaled linearly, nearly all intraordinal regressions scaled non-linearly. The observed non-linear scaling of bone dimensions within this order results from a systematic decrease in intrafamilial allometric slope with increasing body size. A change in limb posture (more upright in larger species) to maintain similar peak bone stresses may allow the nearly isometric scaling of skeletal dimensions observed in smaller sized mammals (below about 100 kg). However, strong positive allometry is consistently observed in a number of large terrestrial mammals (the largest Carnivora, the large Bovidae, and the Ceratomorpha). This suggests that the capacity to compensate for size increases through alteration of limb posture is limited in extremely large-sized mammals, such that radical changes in bone shape are required to maintain similar levels of peak bone stress.

Notes: The introvert of Halicryptus spinulosus bears three kinds of sensilla: buccal papillae, ordinary scalids, and dentoscalids. They are all characterized by bipolar monociliary receptor cells. The former two have apical openings at which the sensory cilia are in close contact with the ambient sea water. The pharyngeal teeth are composed of slender epithelial cells the tips of which are devoid of organelles and a thick cuticle. The anatomy of the muscle arrangement of the pharynx is described. Glands occur at the junction of the pharynx and midgut.

Notes: The book lung surface areas of representatives of six genera were measured and divided by spider prosomal and leg mass and by the product of prosomal length and width to obtain two indexes of book lung area. Both indexes are greatest in species that have the simplest tracheal systems and smallest in those with the most extensive tracheal systems. When species are ordered phylogenetically and the lung area indexes of their hypothetical ancestors computed, a transformational increase in lung area is indicated. Neither the lung area of a species nor its phylogenetic position is significantly related to the general moisture regime of its habitat. The number of leaves in a book lung is positively correlated with both spider size and total lung area. However, leaf number is not correlated with tracheal development and shows no transformational change.

Notes: This paper discusses and corrects ideas in Løvtrup and Løvtrup (J. Morphol. 197:53-62, '88) on how differential growth rates around the aperture cause the gastropod shell to coil at particular angles. The relationship between position relative to the shell apex and growth rate is derived. This lets us understand what information on relative growth rates around the aperture is sufficient to determine the shape of the logarithmic spiral that these growth rates generate. I argue that differential growth rates could not be physiologically controlled precisely enough to regulate apical angle; they passively follow, not actively direct, shell shape.

Notes: The venom apparatus of Ethmostigmus rubripes, a generalized predator, consists of the telopodites of the postcephalic segment, the basal article of which contains the venom gland. Within the gland, venom granules are concentrated in intracellular secretory granules, from which they are discharged into vacuoles in the cytoplasm of the secretory cells and thereafter by exocytosis into the lumen of the gland. A venom duct carries venom to the venom claw, which introduces it into prey via a subterminal pore on the outer curvature of the claw. Pits containing pegs, presumed to be sensory, are concentrated near grooves leading to a cutting ridge proximal to the point of the claw. The venom is toxic both to mammals and insects.

Notes: Meningeal capillaries are unfenestrated. They are made up of endothelial cells that have a pinocytotic caveolae density of 41 ± 11/μm2 and 89 ± 21/μm2 on the abluminal and luminal sides respectively. The total density of intramembrane particles is not significantly different between the luminal and the abluminal membranes; however, the coefficients of partition are significantly different (P〈 0.001). One or two strands of tight junctions occur between adjacent cells but no gap junctions nor desmosomes exist. The density of nuclear pores is less than 3.2/μm2. An abundance of intermediate filaments and free vesicles, some of which are seriated, characterize the cytoplasm. The functional significance of these findings is discussed.

Notes: Vinculin and talin are adhesion plaque proteins which have been shown to interact with each other in vitro. In order to begin to investigate where the talin-binding domain is in vinculin, vinculin was digested with Staphylococcus aureus V8 protease to generate two major fragments of 85 and 30 kDa, and these fragments were purified. Nitrocellulose overlays with 125I-talin and the 125I-85 kDa vinculin fragment and sucrose density gradient centrifugation demonstrated that the talin-binding domain was localized to the 85 kDa vinculin fragment. Quantification of 125I-talin binding in the overlays showed that four times more talin bound to the 85 kDa fragment as compared to intact vinculin. Competitive immunoprecipitation experiments demonstrated that unlabeled 85 kDa fragment, was about three fold more effective at competing for 125I-85 kDa binding to talin than was unlabeled vinculin. These results suggest that the 30 kDa fragment inhibits the vinculin-talin interaction even though the talin-binding domain is localized in the 85 kDa fragment.

Notes: Confluent and proliferatively quiescent T51B rat liver epithelial cells provide a cellular model for the study of epidermal growth factor (EGF) effects in non-neoplastic cells. Immunoreactive calpactin II, a well-known substrate for EGF-receptor kinase, was found predominantly in the cytosol, although a second im-munoreactive pool was found in a Triton X-100-extractable membrane fraction. Stimulation with EGF resulted in a rapid and transient (2-;5 min) formation of ruffles at the cell surface and at the cell-cell contacts. Both calpactin II and filamentous actin were found co-localized at the membrane ruffles. Immunopre-cipitations of membrane-bound calpactin II from 32P-labeled cells indicate a transient EGF-dependent phosphorylation of calpactin II correlating with membrane ruffling. These results suggest a temporal (2-5 min) function for calpactin II at the plasma membrane during the EGF-induced mitogenesis of T51B cells.

Notes: Chlamydomonas cells immobilized on micropipettes were filmed at high-speed (500 f/s) while photostimulated either by one continuous light stimulus or by pulsed light in the frequency range of cell rotation (1 or 2 Hz). Two kinds of photophobic step-up and two kinds of photophobic step-down beat frequency changes without a reversal of flagellar beat were observed after frame-by-frame evaluation of 141 records. So far, a single step-up response, the “shock” response, has been considered the only photophobic response. However, the present results show that the cells always responded to step-up as well as to step-down light stimuli. Either a decrease of beat frequency by step-up was combined with an increase by step-down (type I), or an increase by step-up was combined with a decrease by step-down (type II). Whether type I or type II was observed depended on the preirradiation of the cells. All four responses are blue-light responses with a lag-time of ∼40 ms. Nothing can be said about the photoreceptor site. Regardless, these responses cannot be the basic mechanism for phototaxis, as assumed till now, because the flagella remain synchronized during the flagella beat frequency changes. Even if they are uncoupled before and after stimulation, both flagella respond in the same sense, i.e., either both increase or both decrease their beat frequency. The behavioral relevance of these responses for Chlamydomonas is not yet clear.

Notes: The heterogeneity of mitotic microtubules in dividing sea urchin eggs was investigated by indirect immunofluorescence using five anti-α-tubulin (YL1/2, DM1A, E3B8, D2D6, and 6-11B-1) and two anti-β-tubulin (E6B6 and DM1B) antibodies. These antibodies were divided into four classes in regard to the different immunofluorescent staining patterns: class I, which strongly stained both the spindle and aster (YL1/2, DM1A, E3B8 and E6B6); class II, which strongly stained the spindle but weakly stained the aster (D2D6); class III, which stained only the aster (DM1B); and class IV, which did not stain the mitotic apparatus (6-11B-1). These results suggest that tubulin isotypes are distributed differently in the sea urchin mitotic microtubules and that α-tubulin isotype(s) recognized by D2D6 is (are) localized mainly in spindle microtubules, whereas β-tubulin isotype(s) recognized by DM1B is (are) found only in astral microtubules.

Notes: The assembly of the intestinal microvillus Cytoskeleton was examined during the differentiation of enterocytes along the crypt-villus axis in adult chicken duodenum using light and electron microscopic immunolocalization techniques. Using antibodies reactive with villin, fimbrin, and the heavy chain (he) of brush border (BB) myosin I (110K-calmodulin complex) and rhodamine-conjugated phalloidin as a probe for F-actin, we determined that while actin, villin, and fimbrin were all localized apically along the entire axis, BB myosin I (he) did not assume this localization until the crypt-villus transition zone. In addition to their localization at the BB surface, all four proteins were present at significant levels along the lateral margins of enterocytes along the entire crypt-villus axis, suggesting that these proteins may be involved in the organization and function of the basolateral membrane Cytoskeleton as well. The pattern of expression of the microvillar coreproteins along the crypt-villus axis in the adult was comparable to that seen in the intestine of the late stage chicken embryo and suggests that a common program for brush border assembly may be used in both modes of enterocyte differentiation.