268 FERTILIZATION 



H CLEAVAGE 

 --.•,'■:• . •. U'\: ' !llJ^^ POLAR BODIES 



\* • * .• • . • • •^^ • ^, • . • - 

 ">•,•• . • • • *^"; — : — ; • • * • . . . .'/ 

 ^s; '.'••*.•:.*•.•*•'•*.•.* • •.• ■> • . • .; '^ — M ARG I NAL ZON 



N • * , • . ■ 



^••» -• .- 



^. •••*•• • V^ 



n 



Fig. 136. Organization of germinal disc of the Echidna egg following fertilization. 

 (After Flynn and Hill, '39.) 



cytoplasmic conditions necessary for development, but possesses an active 

 division center which it introduces into the egg at fertilization. Fertilization, 

 therefore, restores the diploid number of chromosomes to the egg and intro- 

 duces an active division center. 



Loeb, J., '13. Loeb believed that two factors were involved in egg activa- 

 tion: (a) Superficial cytolysis of the egg cortex which leads to a sudden in- 

 crease in the oxidation processes of the egg, and (b) a factor which corrects 

 cytolysis and excess oxidation, thus restoring the egg to normal chemical 

 conditions. He placed great emphasis on superficial cytolysis of the cortex 

 with the resultant elevation of the fertilization membrane. 



Loeb suggested that in normal fertilization the sperm brings in a lytic prin- 

 ciple which brings about cortical cytolysis, and a second substance which 

 regulates oxidation. 



For discussion of this theory, consult J. Brachet, '50, p. 138. 



Bataillon, E., '10, '11, '13, '16. Like Loeb, Bataillon emphasized two 

 steps in the activation process of the egg: (a) First treatment, whether it is 

 the puncture of the frog's egg by a fine needle or the butyric acid treatment 

 of the egg of the sea urchin, according to the method of Loeb, causes; ( 1 ) ele- 

 vation of fertilization membrane and the excretion of toxic substances from 

 the egg, and (2) the formation of a monaster, (b) Second treatment, whether 



