608 



DüSTiN further supports his contention that a new generation of 

 sex-cells arise by transformation from ordinary peritoneal cells, by as- 

 serting that he could observe transition forms between the cells of the 

 two types. This is a difficult point to prove. In making observations 

 for my papers upon the sex-cells of Chrysemys, I fully expected to 

 find such transition forms, since this was my preconceived idea when 

 I began the work. A thorough and painstaking search for them utterly 

 failed to convince me of their existence in this or in any later stages. 

 I feel that I am fully justified in maintaining that there is no evidence 

 of such a transformation of peritoneal cells into sex-cells in the case of 

 Chrysemys. We seem to be justified in doubting their derivation from 

 this source in any of the vertebrates, both from the standpoint of ob- 

 servation and from theoretical grounds as well. 



It might be pertinent to the question to call attention to the fact 

 that this alleged period of transformation of peritoneal cells into sex- 

 cells is placed at a stage in which many of the sex-cells have lost 

 their yolk spherules, one of their most characteristic features, and have 

 consequently suffered a slight reduction in size. Dustin's Fig, 16 is 

 altogether unconvincing upon this point. A confusing feature against 

 which one must guard, is the interpretation of the sex -cells that are 

 neither included wholly within the section, nor cut squarely into halves. 

 A portion less than a half might easily deceive, unless the adjacent 

 sections were carefullj'^ searched for the other portion. This question 

 of the transformation of peritoneal cells into sex-cells needs far more 

 investigation than it has been accorded. It is a question that presents 

 so many difficulties of interpretation, that it requires the exercise of 

 the utmost refinement of technique and the utmost breadth of view for 

 its solution. 



Änatomisclie Gesellscliaft- 



Jubiläums-Stiftung. 

 Die in Leipzig gezeichneten Beiträge bitte ich im Laufe dieses 

 Jahres mit der Angabe: „Für die Anatomische Gesellschaft" durch die 

 Post oder mittels Reichsbank-Giro-Konto an das 



Bankhaus Herrn W. Koch jun. in Jena 

 zu übermitteln. 



Jena, Ende Mai 1911. I. A. Der ständige Schriftführer: 



Karl von Bardeleben. 



Der Herausgeber bittet wiederholt, auf Postsendungen dem Worte 

 Jena nichts, insbesondere nicht das Wort „Anatomie" hinzuzufügen. 



K. V. Bardeleben. 

 Abgeschlossen am 18. August 1911. 



FTommannsche Bachdrnckerei (Hermann Fohle) in Jena. 



