ORIGIN OF PRIMORDIAL GERM CELLS 513 



The statement made by Dantschakoff, that the entodermal 

 wander-cells leave the blood enth'ely by the time the embryo has 

 22 somites, is of interest in view of the fact that at that stage the 





®® ^^V:(:r 



■ &■ '■':. , 



© « :■ ■ : ■ — n. p. 



a. op. — r: 



(Sr...; 



4tr — a. pe. 

 ':'v- pr. Ka 



't 



^^jJi^BAJ^t^ C 



Fig. 15 Surface view of a primitive streak stage of a chick embryo, viewed by 

 transmitted light (semi-diagrammatic). Zeiss ocular 2, Zeiss objective A3. This 

 figure is intended to show the point at which the primordial germ-cells arise. 

 The circles a, at the junction of germ wall and area pellucida, indicate this region, 

 a., region in which the primordial germ-cells arise; /j.p., head process; pr.kn., 

 primitive knot; a.op., area opaca; a.pc, area pellucida. 



germ-cells are leaving the vessels of the splanchnic mesoderm 

 and passing into the tissues of the splanchnic mesoderm near 

 the coelomic angle. 



