a spheroidal nucleus as in the spermatozoa of other holothurians (Hodgson and Bernard, 1986; Fontaine and Lambert,1976; Pladellorens and Subirana, 1975a,b). On the other hand, in some species of sea cucumbers, such as C. lubrica (Atwood, 1974) and C. pseudocurata (Atwood, 1975), the spermatids nuclei undergo a process of nuclear elongation during spermiogenesis resulting in a conical shaped head in themature spermatozoon. Other similarities with starfish and sea urchin can be found in the presence of a single mitochondrial ring.