SPERM-EGG INTERACTING SUBSTANCES, I 23 



is evidently something in the ejaculates of many male and female 

 invertebrates which stimulates other members of the same species 

 to shed their gametes ; and it is in part due to the existence of this 

 something that such intensive investigations have been made into 

 the nature and properties of sperm-egg interacting substances. 



Agglutination of spermatozoa by egg water. In the presence of 

 water in which unfertilized eggs of the same species have been 

 standing, 'egg water', spermatozoa come together in clusters 

 (Plate III), which consist of dense aggregates of spermatozoa, 

 usually stuck together by their heads, but sometimes by their 

 tails and even, on occasions, head to tail. The phenomenon has 

 been observed in echinoderms and annelids (F. R. LilHe, 1919), 

 molluscs (Tyler, 19406; von Medem, 1942), ascidians (Minganti, 

 1951), cyclostomes (Schartau & Montalenti, 1941), fish (Hart- 

 mann, 1944; von Medem et al., 1949) and amphibia (Glaser, 1921) 

 and, in some forms, is quite similar to the agglutination of bull 

 spermatozoa in the presence of antisera (Henle et al., 1938). The 

 agglutination of sea-urchin spermatozoa is often spontaneously 

 reversible, the time for reversal depending on the concentration 

 of spermatozoa and of the compound in the egg water responsible 

 for the effect. This compound is called fertilizin or Gynogamone 

 II (G.II). It used to be thought that the unfertilized egg secreted 

 fertilizin into the surrounding sea water. But in 1939 and 1940 

 Tyler & Fox showed that fertilizin was derived from the jelly 

 which surrounds the unfertilized eggs of a number of aquatic 

 organisms. This jelly, which Vasseur (195 1) believes is secreted 

 by follicle cells in the ovary, swells and slowly dissolves in sea 

 water. As the dissolution proceeds, the sperm-agglutinating 

 power, or titre, of the egg water becomes stronger. The process 

 of dissolution can be greatly accelerated, without injury to the eggs, 

 by acidifying the sea water, the degree of acidification required 

 varying in different species. The sperm-agglutinating power of 

 fertilizin so obtained is equal to, or greater than, that from un- 

 treated suspensions in which the unfertilized eggs have been 

 allowed to remain in sea water for a sufficient time for the jelly 

 round them to dissolve. Eggs do not usually yield any more 

 fertilizin once the jelly round them has been removed or has dis- 

 solved. These observations have led to the view that egg jelly is 

 fertilizin and, in support of this contention, Tyler (1942a) re- 

 ported that virtually all the organic material from an electro- 

 c 



