THEORIES OF FERTILIZATION 



269 



it is blood, in the case of the frog, or hypertonic sea water, as used by Loeb 

 in the sea-urchin egg, introduces a catalyzer which converts the monaster 

 into an amphiaster, and in this way renders the egg capable of cleavage. 



Bataillon placed great emphasis upon the exudation (excretion) of sub- 

 stances into the perivitelline space and the elevation of the fertilization mem- 

 brane. He believed that the unfertilized egg was inhibited because of an 

 accumulation of metabolic products and that activation or fertilization led 

 to a release of these substances to the egg's exterior. 



For discussion, consult Wilson, '25, p. 484; J. Brachet, '50, p. 144. 



Lillie, F. R., '14, '19. This author postulated that a substance, fertilizin, 

 carried in the cortex of the egg, exerts two kinds of actions in the activation 

 process: (1 ) An activating, attracting, and agglutinating action on the sperm, 

 and (2) an activating effect on the egg itself. In essence, the egg is self- 

 fertilizing, for the fertilizing substance is present in the egg. The procedure 

 is somewhat as follows: At the period optimum for fertilization, inactive 

 fertilizin (i.e., inactive from the viewpoint of possessing the ability to activate 

 the egg) is produced by the egg. Released into the surrounding water, it 

 activates, attracts, and agglutinates the sperm at the egg's surface. As the 

 sperm touches the egg, it unites with a part of the fertilizin molecule. The 



ENTRANCE 

 OF SPERMJ 



FIRST 

 MATURATION 

 DIVISION- 



SECOND 

 MATURATION 

 DIVISION — 



FIRST 

 MATURATION 

 DIVISION — 



ENTRANCE 

 OF SPERM 



SECOND 

 MATURATION 

 DIVISION — ' 



FIRST 

 MATURATION 

 D IVISION- 



SEGOND 

 MATURATION 

 DIVISION- 



ENTRANCE 

 OF SPERM 



Fig. 137. Maturation divisions of the oocyte relative to time of sperm entrance. (A) 

 Sperm enters the primary oocyte before maturation divisions. In some, e.g., Nereis, 

 Thalassema, Ascaris, Platynereis, Myzostoma, etc., the sperm enters before the germinal 

 vesicle breaks down; in Styela, Chaetopterus, pigeon, etc., the first maturation spindle is 

 formed or forming; in the dog, the condition is somewhat similar to Nereis, Ascaris, etc. 

 (B) Sperm enters the egg after first maturation division, i.e., in secondary oocyte stage 

 {Asterias (starfish), Amphioxus, hen, rabbit, man, frog, salamander, newt, most verte- 

 brates). (C) Sperm enters the egg after maturation divisions are completed, i.e., in 

 the mature egg (Arbacia and other sea urchins; possibly in monotreme. Echidna, on 

 occasion). 



