n8 PROBLEMS OF FERTILIZATION 



containing only immature eggs yields even a trace of 

 sperm-agglutinating substance; and after the eggs are 

 once fertilized and the jelly, which is soaked with the 

 substance, is removed from around the eggs no trace of 

 this substance is ever to be detected from these eggs 

 (cf. also Just on Echinarachnius, 1919). 



The agglutinating substance is secreted by ferti- 

 lizable eggs of Arbacia as long as they remain in a 

 fertilizable condition. However, the jelly membrane 

 of each egg is saturated by the substance, as is readily 

 shown by killing the eggs by heat until they are 

 thoroughly coagulated, when the jelly still continues to 

 give off the substance in large quantities into the sea- 

 water. Loeb (1914) maintains that in Strongylocentrotus 

 purpuratus of California, eggs deprived of jelly lose com- 

 pletely and permanently the power of agglutinating 

 the sperm of its own species; that the jelly alone con- 

 tains the agglutinating substance. This is not the 

 case in Arbacia, for after the unfertilized eggs have 

 been deprived of jelly, either by shaking or by HC1, 

 and washed several times to remove any last traces 

 of jelly, they still continue to produce the agglutina- 

 ting substance. Thus I could show that, whereas the 

 acid solvent which removed the jelly from a given 

 lot of eggs contained only 400 agglutinating units, 

 after a series of washings that represented a dilution 

 of the solvent remaining with the eggs of 12,700,800 

 times, the last washing agglutinated the spermatozoa. 

 In other experiments this process was carried much 

 farther. 



In a considerable number of experiments, not only 

 by myself (1913, 1914), but also by C. R. Moore (1917), 



