182 The Development of the Interstitial Cells of Leydig 



feature of the microscopic picture (Fig. 7). The nucleus is eccentric 

 in its position; around it the cytoplasm is condensed, while at the 

 periphery of the cell, especially at the opposite pole from the nucleus, 

 it is extensively vacuolated (Fig. 8). Many of these vacuoles are irreg- 

 ular in shape with ragged margins, and none of them contain fat. The 

 appearance of the cells suggests that they have been bathed in fluid. 



In unstained sections of material fixed in Flemming's fluid no dark- 

 brown particles were observed in the seminal tubules of pigs of less 

 length than 3 cm. ; with Sudan III no fat could be demonstrated in 

 the tubules of pigs of less length than 8 cm., after which stage it was 

 constantly present in the shape of globules. The germinal epithelium 

 contains no appreciable amount of fat, the granules observed there 

 being of an entirely different nature. We conclude, therefore, that 

 there is no fatty degeneration of the seminal tubules and germinal 

 epithelium in the early stages of the development of the pig's testis, 

 and that, consequently, the hypothesis which attributes the growth of 

 Leydig's cells to fatty degeneration in these situations is incorrect. 



No fat could be demonstrated with osmic acid or Sudan III in Ley- 

 dig's cells of embryos shorter than 14 cm. After this stage it was found 

 in the shape of minute droplets situated in the cytoplasm near the 

 nucleus, but not in the large vacuoles. 



In the young Leydig's cells two structures are found, which, from 

 their morphology and staining reactions, may be classed as centrospheres 

 ( Fig. 9 ) . Never more than one of each kind is present in the same cell, 

 but the same cell often contains both at the same time. The large sphere 

 with the small centrosome is soon lost, while the small sphere with 

 the large centrosome persists through the whole period of embryonic 

 development, though it midergoes certain changes in the late stages. 



In pigs from 2 cm. to 4 cm. long many cells of the germinal epithe- 

 lium are loaded with large granules (Fig. 10). They are hyaline 

 material, resulting from a hyaline degeneration of the cytoplasm of 

 the cells during their conversion into the squamous cells of the tunica 

 vaginalis. 



