103 



inorphosed frof* is reproduced i)i fig. 1, vvliich is drawn after Witschi 

 (1914, fig. A, p. 21.) 



In the literature, dealing with tlie further development of tlie testis, 

 only some scattered remaiks on the testis tubules ai-e to be found. 

 "Damit (i.e. when the stage, reproduced in fig. 1 is reached) haben 

 die Samenkanalchen iin wesentlichen ihren definiti\ en Zustand erreicht" 

 (WiTscHi 1914, p. 20). Then the testis ampullae grow out "zu 

 den bekanuten schlauchförmigen und gewundeuen Samenkanalchen, 

 wahrend sich die Keimzellen ziemlich rascli vermehi-en" (Witschi 

 1914, p. 20). Howevei-, nothing is mentioned about this outgrowth 

 and about the question whether the tubules aie connected with each 

 othei. 



Gaupp describes the form of the testis tubules of the adult frog 

 as follows (1904, 111, p. 307): "Sie beginnen an der Oberflache 

 gerade und mit radiarer Anordnung gegen das Centrum hin, laufen 

 dagegen mehr central vielfach gewunden durch einander. Die radiaren 

 Canalabschnitte dei- peripheren Zone beginnen blind unter der Tunica 

 albuginea, und haufig sieht man hier, wie zwei gesondert entstehende 

 sich mehr central mit einander vereinigen". 



It is my intention to trace how the structure of the adult testis 

 originates fiom the simple one of newly metamorphosed frogs, the 

 latter having been described by Witschi. 



I started with the study of testes of frogs in the beginning of 

 the second year. It proved easiest to get an insight into the form 

 of the testis tubules by studying frontal testis-sections, in which a 

 great number of transvei-sely cut tubules are visible (cf. figs. 2, 3, 

 6, 7, 8, 9). These sections were drawn on transparent paper and 

 then compared. 



In figg. 2 and 3 parts of two frontal sections of the right testis 



(long 1.8, broad 1 mm.) of a com- 

 mon frog with a head-rump length 

 of 3.5 cm. are reproduced. Fig. 2 

 is a section close to the rete ; 

 many tubules transversely cut, 

 are distinctly visible. On tracing 

 the course of the three tubules, 

 designated A, B and C, to the 

 Fig. 2. [)eriphery, we observe that in most 



Section of the testis of a juvenile cases these tubules branch, like 

 frog (beginning of second year), near the fingers of a hand, into a iinujber 

 the rete testis (X 100). of tubules (fig. 3, which is drawn 



after a section close to the periphery) and that all these tubules are 



