476 CATHARINE LINES CHAPIN 



5. FREE-MARTIN 28 CM. T12 



The largest free-martin embryo studied measured 28 cm. 

 (Lillie, figs. 27A and 27B). The male (N19) and female (N28) 

 sectioned for comparison measured respectively 31 cm. and 

 29.5 cm. 



a. Conditions in the normals of this stage 



These specimens differ so little from the smaller normal em- 

 bryos that they will be described but briefly and illustrations 

 seem unnecessary. In the male, the seminiferous tubules are 

 even more contorted than those of T4, and slightly larger. The 

 nuclei, in general, are arranged along the periphery of the sex 

 cords but no lumina are as yet formed. The interstitial material 

 is about equal in volume to the sex cords and contains many 

 interstitial cells. The germ cells which are found in the growth 

 period are even more numerous in N19 than in T4. Most of 

 them are in the later stages of the growth period (i). Otherwise 

 the structures in the 31 cm. male are like those of the 24 cm. cf . 



In the female also some advance may be noted. The medulla is 

 made up more largely of connective tissue stroma, and many 

 more of the medullary cords are degenerating. At the inner 

 ends of the cords of Pfliiger are found many ' nests ' of cells some 

 of which are enclosed by more than one follicular layer. Many 

 germ cells are in the growth period, those in the follicles being 

 more advanced than the others. The germ cells in the follicles 

 are in Schoenfeld's stage i while most of the other germ cells 

 are in stages d, e, etc. No maturation or oogonial mitoses 

 are found. The interstitial, connective tissue stroma is vol- 

 uminous. A few cells in it look like young interstitial cells, but 

 have not been identified with certainty. The albuginea is a 

 little more advanced than it was in the 23 cm. 9 • The rete 

 extends less than half way through the ovary and has no con- 

 nections with the medullary cords. The Wolffian body, and 

 Wolffian and Mlillerian ducts are in the same condition as those 

 of the 23 cm. 9 N25. 



