INITIATION OF DEVELOPMENT IN NEREIS. 1 5 



It appears, therefore, that with KCl, and KCl and heat, 

 washed and unwashed eggs alike will maturate, but that the dry 

 eggs alone respond with cleavage or the production of swimmers. 



Discussion. 



In the egg of Nereis Lillie discovered a substance, feriilizin, 

 which has the property of agglutinating Nereis sperm. This sub- 

 stance may be detected in the water in which the eggs have re- 

 mained for a short time. If, however, the eggs be washed by 

 changing the water two or three times the fertilizin is no longer 

 secreted in detectable quantities, i. e., there is not enough to 

 agglutinate the sperm. Such eggs are none the less fertilizable 

 by sperm, giving off at the time of insemination more fertilizin, 

 all of which is then utilized or completely thrown off during the 

 cortical changes. It therefore follows that at the time of shed- 

 ding the egg is laden with free fertilizin ready for secretion. This 

 conclusion is supported by additional facts. In the first place 

 I have pointed out above that the dry egg or egg in small quan- 

 tities of sea-water is hyper-irritable — that is, if jelly formation 

 may be taken as index. If one inseminates the eggs of Nereis 

 dry or in small quantities of sea-water the jelly formation is 

 extremely rapid. Jelly formation is correspondingly slow in 

 washed and stale eggs. The breeding behavior noted night after 

 night for several seasons is significant: freshly shed eggs at the 

 surface of the sea excite numbers of males to shed their sperm 

 around the shedding or recently spent female. Lillie's experi- 

 ments (Lillie and Just) on this sperm shedding reflex, moreover, 

 prove that the egg loses fertilizin once in the sea-water. The 

 "dry" and "washed" eggs of my experiments, then, are physio- 

 logically different: the dry egg has all its available fertilizin 

 content, the washed egg has secreted part of this substance. 



Lillie has shown that the eggs of Nereis will not fertilize in 

 the tissue juices of the animal; my experiments show also that 

 the body juice of spent females inhibits fertilization. Unlike the 

 washed egg, the "serum" eggs possess fertilizin but its action is 

 inhibited. 



But it is on the basis of experiments on Arhacia that Lillie 

 has developed the fertilizin theory as an explanation of the me- 



