SEX-CORDS AXD SPERMATOGONIA IX CHICK 391 



The cells of the seminiferous cords are of two kiiid? — the 

 ordman' peritoneal cells, issue of the germinal epithelium, and 

 the primordial germ-cells. The fomier are the more numerous 

 and, at this period, can be easily seen to have definite mem- 

 branes. They still preser^'e their cylindrical form, acquired in 

 the formation of the germinal epithelium, and the dark staining 

 round or oval nucleus. 



The primordial germ-cells, although not numerous, are as 

 conspicuous as when obser^'ed in the capillar}' of a 21 somite 

 chick or the root of the forming mesentery- (Swift, '14). They 

 are a Uttle smaller and have lost the characteristic ^'itellus but 

 in all other ways are unchanged. They are still large, have the 

 same clear cytoplasm, large round nucleus and conspicuous 

 attraction sphere. From 2 to 8 of the primordial germ-cells are 

 present in a single cord and there are no signs of division. In 9 

 embryos of this age studied I was not able to find a single pri- 

 mordial germ-cell in mitosis. This last fact is of interest when 

 a comparison is made with the primordial germ-cells in the ger- 

 minal epithelimn of the oyaiy of the same age. It will be re- 

 called (Swift, '15) that during the 8th and 9th da^' in the fe- 

 male the gemi-cells are in an extremely active condition and that 

 the formation of the cortical cords is well under way. 



As regards the stroma only a few lines are necessars'. Only 

 under the gemiinal epithehum is the connective tissue develop- 

 ment considerable. In that region there is a broad band of 

 tissue, the albuginea. In the rest of the gonad, between the 

 seminiferous cords, the small anioimt of stroma still remains 

 embr^'onic in nature, forming a kind of mesenchATual sjTicy- 

 tium. It resembles the mesenchjTne of the mesonephros from 

 which it was originally derived and with which it is still con- 

 nected. 



Four embrj'os aged 11 days were studied. Considerable 

 change has taken place. The testes have increased greatly in 

 size, are rounder, but still have a narrow attachment to the 

 Wolffian body. On examining a section through the testis it 

 will be noticed immediately that the stroma has increased in 

 amount between the seminiferous cords (fig. 1), and that the 



