76 Aetificial Parthenogenesis and Fertilization 



While Figs. 24-26 give a picture of the decay of an egg at 

 room temperature, the start of disintegration at a somewhat 

 lower temperature is represented in Figs. 27-31. The eggs were 

 kept at a temperature between 5° to 10° C. after membrane 

 formation with butyric acid. Many divided and the disinte- 

 gration began later. Drawings were made of a series of differ- 



Pig. 27 



Fig. 28 



Pig. 29 



Fig. 30 



Fig. 31 



Figs. 27-31. — Slow disintegration of the egg of the sea-urchin at low tem- 

 perature. The egg can reach the eight-ceU stage under such conditions. 



ent eggs in incipient disintegration. In all cases this started- 

 with the formation of small drops, usually in the plane of 

 division; the result is always similar to that shown in Fig. 26. 

 We now can answer the question, what is the role of the 

 subsequent treatment of the egg with the hypertonic solution: 

 it serves the purpose of preventing the disintegration which 

 begins at the time of the first cell division. The conditions 



1 for this action of the hypertonic solution will be considered in a 



: subsequent chapter. 



