134 JACQUES LOEB 



CLUSTER FORMATION AND FERTILIZATION 



Lillie's application of the side-chain theory to the problem of 

 fertilization rests on the assumption that the substance which 

 causes the phenomenon he describes as agglutination is indis- 

 pensable for fertilization. This 'fertilizin' is in his theory an 

 amboceptor which must combine at one end with the spermato- 

 zoon at another end with the egg; the 'fertilizin' when in com- 

 bination with the spermatozoon undergoes a change and then 

 fertilizes the egg. It is therefore a substance given off by the 

 egg which in Lillie's opinion causes its fertilization, and not, as 

 we all had hitherto assumed, one or more substances contained 

 in the spermatozoon. 



We have just seen that the substance which causes 1;Jie cluster 

 formation does not come from the egg but is given off by the 

 chorion — or possibly is the chorion itseff which is slowly soluble in 

 sea water. 



We can show in a number of different ways that eggs which 

 have lost or do not possess the power of giving off a substance 

 which induces cluster formation may possess the normal power of 

 being fertilized. If we treat eggs of purpuratus for three minutes 

 in 50 cc. sea water + 3 cc. t^ HCl and wash them about five 

 times in sea water they have lost the power of causing the cluster 

 formation of the sperm of purpm'atus. Such eggs can be fertil- 

 ized immediately after the washing or at any time during the next 

 two or three days if they are kept in the refrigerator. Their 

 power of being fertilized is not in the least impaired. One hun- 

 dred per cent of the eggs were invariably fertilized and the fertil- 

 ization took place instantly aftfer the addition of sperm. Prac- 

 tically all the eggs developed. The membrane was slightly 

 abnormal which was an after-effect of the acid treatment. The 

 power of the eggs of being fertilized remains unimpaired while 

 their power of giving off substances which cause cluster formation 

 is completely and permanently lost. 



When we treat the eggs with a fatty acid instead of with a 

 mineral acid they form, when transferred to normal sea water, a 

 fertilization membrane. The fatty acid also dissolves the chorion 

 and such eggs when washed afterwards lose their power of indue- 



