82 Specificity in Fertilization 



by the mature eggs of the sea urchin piirpuratus and 

 franciscanus. In studying these results the reader must 

 keep in mind first that all these experiments were made 

 in a NaCl solution and second that it requires a stronger 

 influence to activate the spermatozoa of the starfish, 

 which are not motile at first even in sea water, than 

 the sea urchin spermatozoa which are from the first 

 very active in such sea water, and which may there- 

 fore be considered as being at the threshold of activity 

 in pure NaCl solution. 



Wasteneys and the writer (in experiments not yet 

 published) did not succeed in demonstrating an activat- 

 ing effect of the eggs of various marine teleosts upon 

 sperm of the same species. 



4. F. R. Lillie^ has studied the very striking phe- 

 nomenon of transitory sperm agglutination which 

 takes place when the sperm of a sea urchin or of 

 certain annelids is put into the supernatant sea water 

 of eggs of the same species. If we put one or more 

 drops of a very thick sperm suspension of the Cali- 

 fornian sea urchin S. purpuratus carefully into the 

 centre of a dish containing 3 c.c. of ordinary sea water 

 and let the drop stand for one-half to one minute and 

 then by gentle agitation mix the sperm with the sea 

 water the mass of thick sperm which is at first rather 

 viscous is distributed equally in sea water in a few 



' Lillie, F. R., Science, 1913, xxxviii., 524; Jour. Exper. ZooL, 1914, 

 xvi., 523; Biol. Bull., 1915, xxviii., i8. 



