XXV 



ARTIFICIAL PARTHENOGENESIS, IN THE EGGS OF THE 



STARFISH 



1. The experiments on artificial parthenogenesis in starfish 

 differ in an essential point from those in the sea-urchin. The 

 sea-urchin egg undergoes maturation and remains at a state 

 of rest while in the ovary. The causation of development 

 means, therefore, a transition from the resting state to an active 

 state, and this is accompanied by a rapid increase in the rate 

 of oxidations. 



The conditions in the starfish egg are different. When these 

 eggs are taken out of the ovary they are as a rule immature. 

 As soon as they are laid, a number of eggs, which varies with 

 the individual starfish, begin to mature. Not until one or both 

 polar bodies are thrown out can a spermatozoon enter. As 

 soon as this critical stage is reached the egg can be fertilized by 

 sperm. If it is not fertilized by sperm at that time it perishes 

 in a few hours. There is then this difference between the state 

 of the sea-urchin egg and that of the starfish egg at the time 

 of fertilization: The starfish egg is in a state of activity since 

 the maturation divisions are just completed, while the sea- 

 urchin egg is at rest. This finds its expression in the fact that 

 Wasteneys and I found that the entrance of a spermatozoon 

 into the starfish egg does not increase the rate of oxidations.' 

 It harmonizes with this result that the writer found that the 

 process of maturation of the starfish egg requires conditions 

 similar to those for the development of the sea-urchin egg : If 

 oxygen is removed from the sea-water or KCN is added the eggs 

 remain immature. Moreover, in an alkaline solution the eggs 

 ripen more rapidly than in a neutral or acid solution. 



1 Loeb and Wasteneys, Archivf. Entwicklungsmechanik, XXXV, 655, 1912. 



249 



