98 BENJAMIN H. WILLIER 



much thickened basement membrane. The outer lamellae are 

 loosely arranged and blend with the connective-tissue fibers of 

 the stroma. 



Within the membranous wall the supporting epithelium is 

 arranged in such a manner that two distinct stages in organiza- 

 tion may be. recognized. The first stage is illustrated in the 

 gonads from cases 44 and H-46 (fig. 12, s); here the nuclei of the 

 supporting epithelial syncytium are very regularly arranged into 

 a single layer. The long axes of the oval nuclei are perpendic- 

 ular to the tubular wall, and from the inner ends of the nuclei 

 fihny strands of cytoplasm extend toward the center of the 

 tubule. This syncytium of epithehal cells is identical with the 

 syncytium found in the seminiferous tubules of late foetal 

 testes and young postnatal testes (compare with figures 7 and 

 8), with one important exception, namely, the complete absence 

 of germ cells in the free-martin syncytium. 



The second stage, illustrated by case H-37 (fig. 11, ss), shows 

 more advanced differentiation in the male direction, as the 

 supporting epithehal syncytium has become resolved into a 

 Sertoli-cell syncytium as in the adult normal testis (compare 

 with fig. 13, ss). The cytoplasmic substance of the syncytium 

 stains lightly, and structurally it appears as a loose meshwork 

 of branching strands of cytoplasm. These strands have more or 

 less of a fibrillar structure, the fibrils of which are very delicate 

 and in some cases not very sharply defined. The cytoplasm is 

 continuous throughout the tubules except as interrupted by the 

 scattered nuclei and spaces. The oval nuclei, which lie at 

 various levels in the syncytium, are characterized by their dis- 

 tinctive nucleoli. The nucleolus is a comparatively large, nearly 

 spherical body which takes a deep chromatic stain. Apart from 

 the nucleolus, the chromatic material is very scanty. The 

 Sertoli-cell sjmcytium is structurally alike in both the free- 

 martin seminiferous tubule and the normal seminiferous tubule 

 of the adult bull, except male sex cells are absent in the former. 

 The structure of the normal syncytium can be very beautifully 

 demonstrated at the zone of junction between a seminiferous 

 tubule and a straight tubule (fig. 13, ss). In this zone the 



