286 INTRODUCTION TO CYTOLOGY 



Heilbrunn (1920) shows that the egg of Cumingia can be induced to 

 undergo maturation by agencies which release the fluid cytoplasm from 

 the restraint of the tough vitelline membrane. If the membrane be 

 swollen, elevated above the egg surface, ruptured, or removed the 

 maturation changes begin at once. 



The sickliness and death of those eggs given only the first treatment 

 Loeb thought to be due to the continued action of the cytolytic agent. 

 Against this conception it is urged by F. R. Lillie that since any activated 

 egg not developing normally cytolyzes sooner or later from internal causes, 

 it is more probable that the sickliness and death are due to some internal 

 cause resulting from activation, and points out that such a conclusion is 

 supported by the cytological phenomena in eggs activated by Loeb's 

 method. To these phenomena we may turn for a moment. 



Eggs which have been given the first treatment alone do not begin to 

 disorganize for many (12 to 24) hours. During this period Herlant (1917) 

 has observed the following events. After the formation of the mem- 

 brane and a hyaline zone, alterations cease, and the nucleus becomes the 

 seat of a series of conspicuous changes. The nuclear membrane dissolves, 

 and around the chromosomes there is formed a monaster (one-poled 

 group of achromatic fibers), but no amphiaster develops. The chromo- 

 somes divide but do not separate, and although the cytoplasm becomes 

 active no cytokinesis ensues. The chromosomes then return to the 

 resting condition. This process is repeated several times, the nucleus 

 increasing in bulk each time, but it soon becomes very irregular and the 

 egg ultimately breaks down by general cytolysis. The second treatment 

 (Loeb's method) in some way gives the egg the capacity to divide regu- 

 larly. Morgan (1899) and Wilson had long before shown that such 

 treatment with hypertonic sea water causes aster formation in the 

 unfertilized sea urchin egg. Herlant shows that one of these asters and a 

 second aster formed in connection with the egg nucleus together form an 

 amphiaster, normal division then ensuing. 



In the light of these facts it seems evident that the death of the egg 

 after the first treatment alone is not due to the continued action of the 

 cytolytic agent employed, but rather to irregularities in the activation 

 processes aroused by the cortical changes in the absence of a proper 

 coordination of nuclear and cell division. The second treatment pro- 

 duces a regulatory effect, partly through aster formation, resulting in 

 normal development. This recalls Boveri's morphological theory of 

 normal fertilization. 



Direct Analysis of the Fertilization Process. — In contrast to the theory 

 that the spermatozoon contributes organs (Boveri) or substances (Loeb) 

 necessary for the activation, Lillie (1919, Chapter VII) regards the egg 

 itself as an " independently activable system." "The egg possesses all 

 substances needed for activation; the spermatozoon is an inciting cause 



