386 CHARLES H. SWIFT 



neighboring cells. The cells, then, are apt to be stellate in 

 appearance and the whole tissue to resemble a loose syncytium. 

 This stroma, more voluminous in the case of the left gonad, 

 fills up the region between the concave germinal epithelium and 

 the Wolffian body and, in fact, forms most of the area of the 

 gonad. 



This stroma is denser just under the epithelium, and from 

 this region, if the sections happens to be right, a narrow cord 

 may be seen to extend obliquely towards the Wolffian body. 

 This cord, the result of a condensation of naesenchyme tissue, 

 is known as a rete cord or cord of uro-genital union and must 

 not be confused with the sexual cord, which arises later and iri a 

 different way. According to Firket ('14) there are 16 of these 

 cords. It is not my intention to enter into the origin of these 

 cords or to engage in the controversy as to their origin, for an 

 excellent review of all the facts and literature will be found in 

 Firket's ('14)- article. 



The third tissue present in the gonad is made up of primordial 

 germ-cells. 



The cells are easily seen, for their great size, large nucleus, 

 and clear cytoplasm make them conspicuous in the chick as in 

 all the other forms in which they have been observed. They 

 merit, however, a more extended description. 



The primordial germ-cells do not form a compact or continu- 

 ous tissue in the indifferent gonad of 5 days, but are present, 

 usually, as isolated cells or groups of several cells in the germinal 

 epithelium and subjacent stroma (Swift, '15). They may be 

 even seen in the root of the mesentery subject to the same 

 arrangement. 



These primordial germ-cells are, at a glance, seen to be dif- 

 ferent from the other tissues of the gonad. Although present 

 in the epithelium and stroma of the genital hillock yet I have 

 never seen a stage which could be called a transition between 

 them and the surrounding cells, for in addition to their large 

 size, great nucleus and clear cytoplasm, they possess even at this 

 late date (5 days) many droplets of vitellus in the cytoplasm 

 and a conspicuous attraction-sphere (Swift '14 and '15). The 



