PAR THENOGENESIS 



or others start development in the naturally parthenogenetic 

 egg. Until more data are available, we can not go beyond 

 such general statements as to the probable cause of natu- 

 rally occurring parthenogenesis. 



As to experimentally induced parthenogenesis, however, 

 the experimental findings suffice for an attempt at formulat- 

 ing a theory. And indeed, many theories have been prof- 

 fered. With respect to one of these which became the most 

 widely known, one notes a curious, even an anomalous 

 situation. Although the data on induced parthenogenesis 

 indubitably show that one means alone suffices to call forth 

 development in the eggs studied, including those of sea- 

 urchins, this theory, whose founder is Loeb, runs counter to 

 these findings, including most of its author's, in explaining 

 the phenomenon as due to the action of two distinct means 

 because of the one fact that with a certain method, eggs of 

 sea-urchins develop in more nearly normal manner after 

 treatment with two means. 



Since the interpretation of the induction of partheno- 

 genesis in sea-urchins' eggs by the double method came 

 finally to be the most widely accepted theory of fertilization 

 embracing all animal eggs, we must examine it here. In 

 this interpretation it is contended that butyric acid or any 

 other agent which calls forth membrane "formation" tends 

 to destroy, i.e., superficially cytolyze, the egg; and that such 

 an agent acts as do haemolytic agents, those that destroy 

 red blood cells. The second agent, it is held, corrects the 

 destructive action of the first. This interpretation of cer- 

 tain experimental findings on eggs of sea-urchins became 

 the famous "superficial-cytolysis-corrective-factor" theory 

 for experimental parthenogenesis and for fertilization. The 

 question now arises: Do the experimental findings on which 

 it is based, actually permit this interpretation.^ 



Eggs in sea-water, no matter from what species of animal 

 they are, eventually die if they are not fertilized, that is, 



22J 



