STUDIES IN ARTIFICIAL PARTHENOGENESIS. 1 

 I. MEMBRANE ELEVATION IN THE SEA-URCHIN EGG. 



LEWIS V. HEILBRUNN. 



Introduction. The ultimate goal in the study of artificial 

 parthenogenesis is the discovery of the chemical and physical 

 forces which are assumed to cause the initiation of development. 

 The pioneer workers on the problem (Tichomiroff, O. and R. 

 Hertwig, Morgan) were content to regard the phenomenon as 

 the result of a stimulus which arouses the egg from its resting 

 condition. But the present tendency, thanks to the work of 

 Loeb and his school, recognizes that such a theory is merely a 

 cloak for our ignorance, it is little more than a restatement of the 

 problem. For it gives us no information as to the real nature 

 of the assumed stimulus, or in what manner it effects its action. 

 The foremost difficulty in the way of a physical or chemical 

 interpretation is the wide range of chemicals and forces all of 

 which are capable of producing artificial parthenogenesis. None 

 of the theories recently advanced seems capable of explaining 

 all or nearly all of the facts. As a result there has been of late 

 again a return to those vague ideas which challenge attack. 



In almost all hypotheses of artificial parthenogenesis, the 

 process, as a result of which a membrane is either pushed out 

 or formed "de novo" around the egg, plays an important role. 

 This so-called "membrane formation" is readily observed in the 

 egg of the sea-urchin, and it is in Arbacia that I have attempted 

 to study it. I am indebted to Prof. T. H. Morgan for the use of 

 a Columbia table in the Marine Biological Laboratory at Woods 

 Hole, Mass., where I spent the summer of 1912. 



The form studied was Arbacia punctulata (Gray). The 

 nomenclature of the membranes of the sea-urchin egg is some- 

 what varied, and it will be necessary to decide on a series of 

 terms, which, for the sake of clearness, shall be exclusively 



1 From the Cornell University Laboratory of Embryology. 



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