EGG SECRETIONS OF ARBACIA AND ASTERIAS 461 



From these facts, Lillie deduced his 'side chain' theory of 

 fertilization, in which he appHed Ehrhch's conceptions to the 

 subject at hand. He postulates that spermatozoa are chem- 

 ically unable to unite directly with the egg, but that a third body, 

 or amboceptor — in this case, fertilizin — is necessary to join them. 

 Fertilizin, he believes, has two side chains, an ovophile group 

 which can unite with a side chain of the egg, the egg receptor, 

 and a spermophile group, which can unite with a sperm receptor. 

 Fertilization may be blocked by 1) absence of the amboceptor; 

 2) occupation of either side chain by a foreign body; 3) occupation 

 by similar means of either sperm or egg receptor. Further, 

 ''The sperm activates the fertilizing substance (fertilizin) already 

 present in the egg. The egg is self -fertilizing (Lillie, 14, p. 

 587)." 



II. CONCERNING THE FACTUAL BASIS OF THE FERTILIZIN THEORY 



The fertilizin theory is founded upon three essential elements: 

 an amboceptor, an egg receptor, and a sperm receptor. The 

 presence of the amboceptor, Lillie believes, is indicated by a. 

 sharply defined reaction-agglutination of the sperm. This re- 

 action is considered ('15) only as a visible, but not essential,, 

 symptom of a fundamental physicochemical change in the sper- 

 matozoa themselves. It is possible that in many species the egg; 

 secretion produces a significant change in the sperm without 

 agglutinating them. The presence of sperm receptors, according 

 to the same author, is indicated, among other things, by the 

 Godlewski phenomenon, in which the inhibitory effect of foreign 

 sperm is explained as due to the occupancy of the normal sperm 

 receptors. The presence of an egg receptor he has been unable 

 to demonstrate directly. It is, however, indicated by other in- 

 hibitors which effectively block the fertilization reaction. 



A. Concerning egg secretions in general 



The observations of Lillie with regard to the egg secretions of 

 Nereis and Arbacia have been extended by several workers upon 

 the same and other forms. 



