396 



CHARLES H. SWIFT 



dria were found grouped around the attraction-sphere in a 

 characteristic manner. It is a striking and suggestive fact that 

 the same change occurs in the male line. In all the primordial 

 germ-cells in the sexual cords of the male chick, up to and in- 

 cluding the 1 1 day stage, the rod shaped and granular mitochon- 

 dria are evenly distributed (fig. 1). This arrangement also 







str 



Fig. 3 Portion of a, transverse section through tlie right testis of a 15 day 

 chick embryo. This section shows a massive seminiferous cord, composed of 

 primordial germ-cells, spermatogonia and peritoneal cells. One of the germ- 

 cells is dividing. The spermatogonia, at the left, contain the characteristic 

 mitochondrial crescent which serves to identify them. 



holds for the germ-cells of the 13 day embryo and for the few 

 present in the 15 day stage. 



Thus, beginning with the 13 da}^ embryo, a new mitochondrial 

 arrangement is noticed; the mitochondria are grouped around 

 the attraction-sphere, so that they form a granular crescent or 

 cap on the nucleus, depending upon the plane of the section 

 (figs. 3, 4, 5 and 6). As was stated above and in a former 



