140 SECRETS OF ANIMAL LIFE 



frog, artificial parthenogenesis, followed by normal 

 development, can be induced in egg-cells which 

 invariably require fertilization in the ordinary 

 course of nature. Professor Jacques Loeb's chief 

 method is to subject the ova, say of sea-urchin 

 or starfish, first to the influence of some fatty acid, 

 like butyric, which leads to oxidations in the cortex 

 of the egg, the formation of a membrane of fertiliza- 

 tion, and so on. The egg is activated, and if the 

 process continues it ends in disintegration and death. 

 But if at an appropriate time the activated egg 

 is subjected to hypertonic sea-water, this acts as a 

 corrective of the impending dissolution, and brings 

 the egg back to a safe path of normal development. 

 Professor Yves Delage's chief method is to subject 

 the ova of sea-urchin or the like to the combined 

 action of tannin and ammonia, the former tending 

 to coagulate, the latter tending to liquefy, the 

 colloid substances which make up the egg. Most 

 of the ova, when restored to sea-water, develop 

 and form normal larvae; in two or three cases the 

 adult form has been reached. Bataillon's chief 

 method is to prick frogs' eggs with a very fine 

 stylet of glass or platinum, and then wash them 

 with blood. The first event provokes activation; 

 the second event allows the entrance of an organic 

 center (a blood corpuscle, and not necessarily a 

 frog's!) which initiates a well-balanced ovum- 

 segmentation. Two or three parthenogenetically 

 developed frogs have been reared ; they are normal, 

 and of both sexes. 



