ORIGIN OF PRIMORDIAL GERM CELLS 511 



tendencies she called them entodermal wander-cells. They ap- 

 pear at first in groups, between the germ wall entoderm and ecto- 

 derm, anterior to the forming embry^o, before mesodermal tissue 

 has grown out into that region. They then enter the mesoderm 

 and forming blood-vessels, and, either by their own amoeboid 

 powers, or aided by the vascular circulation penetrate into every 

 part of the area vasculosa and embryo. Although for some time 

 in the vascular system yet they are not blood cells as is evidenced 

 by their appearance, origin and fate. Some of these entodermal 

 wander-cells enter the embryonic tissues, leaving the blood-\'essels 

 by their power of diapedesis, and degenerate. Others undergo 

 a like fate in the blood-vessels themselves. The remainder dis- 

 appear from the blood-vessels and by the time the embryo has 

 22 somites all have gone. Although the fate of those which do 

 not degenerate is unknown, yet Mile. Dantschakoff believes that 

 they have no share in tissue formation. 



These entodermal wander-cells of Dantschakoff are in reality 

 the primordial germ-cells of the chick. There is a close agreement 

 as far as origin is concerned, for I also find that the germ-cells 

 originate from certain cells of the germ-wall entoderm near its 

 junction with the area pellucida. I find also that they are pro- 

 duced during the primitive streak stage and in the embryo pos- 

 sessing at least 3 somites. 



These germ-cells arise in a region of the germ-wall anterior to 

 the forming embryo and also antero-lateral. This region, just at 

 the junction of area pellucida and germ- wall, has roughly the 

 shape of a crescent, the concavity being turned towards the em- 

 bryo; the horns extend caudal ward on either side (fig. 15). In 

 this crescent shaped region many of the germ-wall entodermal 

 cells resemble the germ-cells (fig. 14). They have the round nu- 

 cleus, great quantity of yolk and the large conspicuous attrac- 

 tion-sphere. 



That these particular germ-wall entodermal cells are producing 

 the primordial germ-cells, is proven by the fact that in the primi- 

 tive streak stage, before the appearance of mesoderm anterior 

 to the embryo, the germ-cells are grouped in the space between 

 entoderm and ectoderm in this immediate neighborhood; the 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 15, NO. 4 



