100 



of testes of inouse-embrjos of 9 — 17 mm. length. The fundamental 

 form of the embi-jonic testis fubiile is a simple n-like lube, of which 

 the convex side is dii-ected towards the peripheij and of which the 

 extremities are connected with the future rete testis. A number of 

 these tubes are placed serially behind each other; anastomoses between 

 the arciies and double-airhed, m-like tid)es occur also. The plane of 

 the arch is perpendicular to the longitudinal axis of the testis. 

 Tubules, terminating in Idind ends, were rai-ely found. In the caudal 

 part of the testes of embryos of 13 mm. and smaller a so-called 

 ,, canal-complex" occurs, from which later on — for in older testes 

 more arches are to be found than in younger ones — additional 

 arches probably develop. The tul)ules number from 10 to 13 in the 

 mouse. After the ,,caual-coniplex" has disappeared, the longitudinal 

 growth of the testis-tubules sets in and then the tubules begin to coil 

 strongly. From the longitudinal stem, originally epithelial, the rete 

 testis develops. 



In a second paper dk Buri,et (1921) traced the morphology of a few 

 Mai'supialian testes {Perameles ohesuJa, Diclelphi/s spec, Hahnatiirus 

 Bennetti). The single-arched tubule was found again ; in Perameles 

 the testis (embryo of 50 n)m.) is still more simplj built than in the 

 mouse; the testis of Didelphijs (embryo of 20 mm.) is composed of 

 two long, strongly twisted tubules. These tubules are verj' numerous 

 in Halindiurus (embryo of 105 mm.), where they vary from 200 

 to 300. 



Starting from the al)ove investigations it was but natural to trace 

 in one of the representatives of the other Vertebrate groups, how 

 tlie shape of the adult seminiferous tubule derives from the embryonic 

 one. After consulting Dr. H. M. de Hcrlet, to whom I wish to 

 express my thanks for his interest in this work, I chose the com- 

 mon Frog, Nana fuse a Uösel. As it appeared during the investi- 

 gation that in immature frogs the course of the vasa efferentia, 

 the ducts through which later on the spermatozoa pass to the kidney, 

 show ditferent peculiarities, I decided to communicate simultaneously 

 a few remarks concerning the course of these channels in immature 

 frogs in the beginning of their second year. 



Material and methods. 



AH specimens of the common frog were caught at Bilthoven 

 (near Utrecht) in Sept. 1920. The smallest, immatuie frogs measured 

 2.8 cm. (from the head to the rump), the largest, adult spec. 6.3 cm. 

 According to Gaupp (1904, III, pp. 298 — 300) frogs measuring circ. 



