ABSTRACT
Phagocytes of eight echinoderm species and five non-echinoderm invertebrates were examined in vivo with respect to their ability to form syncytium. The finding is that the phagocytes of all echinoderms examined fuse extensively with one another, while those of four non-echinoderm species, including sipuncula, echiuroid, bivalve and insect, show no such activity. The ascidian species examined, on the other hand, formed syncytium less extensive than the echinoderm ones in both shape and frequency.
The extraordinarily fusogenic nature of the echinoderm phagocytes in in vivo is discussed in relation to the fragile nature of the echinoderm body and the consequent necessity for a quick defense requirement.
