THE LIPIDS OF SEA-URCHIN SEMEN

The constitution of the lipid material present in semen has received very scant attention. No reference appears in the literature relating to the component fatty acids of semen lipids, although the presence of neutral fat, free fatty acid, free and combined sterols, phosphatides, and sphingomyelin has been reported by Wood-house (1928) in the sex organs of domestic animals and of humans; likewise, Sakaki (1913) reported the presence of phosphatides and sphingomyelin in the human placenta; Sano (1922) reported the presence of these phosphatides in the fresh ' sperm freed from membranes and connective tissue ' of the cod, porgy and salmon. More recently, Lardy & Phillips (1941), in an investigation of the sources of energy for bull spermatozoa, showed that the phospholipid content of both semen and spermatozoa decreased when incubation was carried out in the absence of extra-cellular substrates but in the presence of oxygen. Our knowledge of the physiology of sea-urchin spermatozoa is primarily due to Rothschild and co-workers who have shown (see Rothschild, 1951) that sea-urchin spermatozoa differ from those of mammals, in which the energy for motion i