C. B. METZ 35 



water and an "adjuvant" (Plate I). This fertilizin-adjuvant ag- 

 glutination has been reported in ten species of starfish (Metz, 

 1945, 1954b; Metz and Donovan, 1950; Dan, 1954a). In this 

 reaction the fertilizin is species specific; the adjuvant is not spe- 

 cific. The first adjuvants found were poorly defined materials 

 ( animal sera, hen's egg white ) , but subsequent study ( Metz and 

 Donovan, 1950; Metz, 1954b) revealed that alkali, amino acids, 

 peptides, SH containing substances, versene, and other metal 

 binding or chelating agents were effective adjuvants. Since metal 

 binding is a common property of these diverse agents and since 

 the adjuvant action is inhibited by addition of metal cations 

 (Metz, 1954b), it appears that the essential function of the ad- 

 juvant is a removal of metal ions. This view explains certain earlier 

 observations. Among these is the report ( Metz, 1945 ) that dena- 

 tmation by heating or ultraviolet radiation increases the adjuvant 

 action of egg white. This enhanced action probably results from 

 exposure of additional SH groups (Mirsky and Anson, 1934). 



The adjuvant apparently acts upon the sperm, not upon the 

 fertilizin in the fertilizin-adjuvant agglutination reaction. This 

 follows from the fact that sperm, after removal from the adjuvant, 

 can agglutinate on addition of fertilizin. In one experiment 

 (Metz, 1945) spenn were washed free of adjuvant (hen's egg 

 white ) with sea water. In another ( unpublished ) the alkali used 

 as the adjuvant was neutralized with acid. This experiment is 

 summarized in Table II. In both of these experiments the sperm 

 reverted rather rapidly to the nonagglutinable condition. This 

 is explained by the addition of metal ions ( sea water ) in the first 

 experiment. The action of alkali in the second experiment is as- 

 sumed to involve binding metal ions as insoluble or un-ionized 

 hydroxides. Upon addition of acid these hydroxides would be 

 neutralized and thus free the metal cations. Presumably the sperm 

 would remain agglutinable if the adjuvant (and bound met- 

 als) were washed away with salt solutions lacking the offending 

 metal ions. 



These experiments show that the adjuvants act primarily upon 

 the sperm. Accordingly the fertilizin must be multivalent. This 

 view is supported to the extent that starfish fertilizin can be con- 



