Re-examination of a Supposed Case of Specific Cell Adhesion

Abstract

SPECIFIC adhesion of sponge cells, such that only the cells of a single species will adhere together, has been claimed by many workers^1–3. Indeed, the particular specific behaviour which has been reported³ for mixtures of cells from pairs taken from Haliclona occulata, Halichondria panicea, Microciona prolifera and Clione celata has been regarded as one of the most remarkable examples of specific adhesion or cell recognition, Sara^4–6 has tested combinations of other species of marine sponge for specific adhesion without success. In all work on sponge cell aggregation, the recognition of the species type of the cells in the aggregates has depended on subjective observation of the colour of the aggregate. I find this criterion defective, for it is extremely easy to fail to observe a small proportion of cells of one colour and species type scattered in a mass of cells of a different colour and species type. Furthermore, only a proportion of the cells of highly coloured sponges may carry the pigment distinctive of a species, so that it is uncertain what happens to the unpigmented cells.