DEVELOPMENT OF GONADS AND TEANSFOR- 

 MATION OF SEX IN THE FEOG 



DE. EMIL WITSCHI 

 Lecturer in Zoology in the TJnivki;sitv of P. ai.k. Swit/.i-ki-and 



In the following paper I intend to c a summary of 

 the sexnal problems in the froii', as tliey icsult from de- 

 scriptive and analytic research. Richard llertwig's suc- 

 cessful experiments on sex-determination have directed 

 the attention of investigators to this object. From 1911 

 to 1913 the writer was fortunate enough to have the oppor- 

 tunity of working in Hertwig's laboratory and since then 

 the investigations have been continued at the zoological 

 laboratory of Basle University. The present paper is a 

 brief summary of the development of the sexual char- 

 acters. In a later publication we hope to ex]ilain tlie ex- 

 periments on sex-determination and to (leseril)e the 

 chromosome cycle. 



In the number of this journal for July-August, 1920, 

 Dr. W. W. Swingle has published an interesting study 

 on Neoteny and the Sexual Problem," and in the Feb- 

 ruary number of the Journal of E.rpv r'nucutal Zoology 

 the same author has described ifi uicaler detail the 

 developmental history of the male -onad of liana cates- 

 hiana. In both communications Swinule has disputed the 

 correctness of the work of tlie lIei-twi,o- M'hoo\. The fol- 

 lowing explanations may 1»e reuarded a- a reply to 

 Swingle's critical renuirks. 



A. The Sexual Glaxds 

 1. Morphologif of the Undiiferentiatod Gland.— The 

 gonad of larvip 22 mm. in length, just l)et^>re sex-differ- 

 entiation takes ].]aee. lias the foll.nvinu' structure. A 

 sim])le u'ei-niinal e])itlieliuni encloses tlie central primitive 

 gonad cavity. Five to seven sex cords, Imdding from the 



