C. B. METZ 33 



reversal of agglutination in the echinoids and the necessity of an 

 "adjuvant" or second factor in asteroids. 



Spontaneous Reversal of Agglutination. Lillie (1913b) ob- 

 served that upon mixing Arbacia sperm and egg water the sperm 

 clumped together forming microscopically visible agglutinates, 

 but within a few minutes these clumps broke down, releasing the 

 individual sperms. Similar spontaneous reversal of agglutination 

 has been reported in most of the echinoids so far examined. Lillie 

 ( 1913b) showed that following such reversal of agglutination the 

 sperm could not be reagglutinated by further addition of egg 

 water. Evidently then, the sperm surface is altered in the course 

 of agglutination and reversal. Tyler ( 1941 ) considered several 

 possible explanations for this spontaneous reversal and failure 

 of reagglutination and he concluded that the fertilizin molecule 

 was probably split by action of the sperm into fragments each 

 possessing only a single reactive group. Such univalent fragments 

 should remain in combination with and saturate the antifertilizin 

 groups of the sperm surface without causing agglutination. Fur- 

 thermore, the univalent fragments should protect or block the 

 sperm antifertilizin from reaction with the normal, multivalent, 

 agglutinating fertilizin (see Fig. 1 for schematic illustration). In 

 support of this view Tyler (1941) and Metz (1942a, 1954c) have 

 shown that a number of agents (heating, proteolytic enzymes, 

 x-radiation or ultraviolet radiation, H2O2 oxidation) will convert 

 fertilizin to the univalent form. Such fertilizin will not agglutinate 

 sperni but it will combine with sperm and render it unagglutina- 

 ble by untreated fertilizin. As a final parallel with antigen-anti- 

 body systems Tyler (1945) showed that rabbit antibody could 

 also be converted to a nonagglutinating, univalent form. 



Fertilizin Agglutination of Starfish Sperm. Some early inves- 

 tigators (Glaser, 1914; Woodward, 1918) reported direct agglu- 

 tination of starfish sperm by specific egg water, but others (Just, 

 1930; Loeb, 1914; Tyler, 1941; Metz, 1945, 1954b; Metz and 

 Donovan, 1950; Dan^ 1954a) have been unable to confirm this 

 result in the same and other species. Conditions in the starfish 

 were clarified by the discovery (Metz, 1944, 1945) that strong 

 agglutination results when sperm are mixed with specific egg 



