XXV 



ARTIFICIAL PARTHENOGENESIS IN THE EGGS OF THi: 



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. 1 

 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, Archiv f. Entwicklungsmechanik, XXXV, 555, 1912. 



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