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BENJAMIN H. WILLIER 



irregularly arranged. In testes from a 7-cm. (N 10) and a 12.7- 

 cm. (T 16) embryo some slight degree of organization is recog- 

 nizable. A definite tubule wall is evident, and the supporting 

 epithelial cells are formed in a sj^ncytium, the nuclei of which 

 are becoming arranged into layers, some having three layers, 

 others two layers. From the inner ends of the nuclei, which 



Fig. S Portion of a transverse section through a testis of a young male calf 

 (six months?), Bos 12. gc, primordial germ cell; ss, syncytium of supporting 

 epithelial cells; i, interstitial cells. X 307. 



show a tendency to be arranged with their long axes perpen- 

 dicular to the tubule wall, strands of cytoplasm extend toward 

 the center of the tubule. The organization of the syncytium 

 progresses in the older testes, until finally a striking degree of 

 regularity is shown in testes from 31-cm., 61-cm., 89-cm. embryos 

 and in testes from young calves (2 and 12 days, and 6 months). 

 Figures 7 and 8 show the nuclei of the supporting epithelial 

 syncytium arranged in a single distinct layer, closely applied to 

 the wall of the tubule. The long axes of the oval nuclei are 



