510 



CHARLES H. SWIFT 



Fig. 13 Portion of a transverse section through a 19 somite chick embrj'o. 

 Aleves' fixation and Meves' iron-hematoxylin stain. X 1125. pr.o., primordial 

 germ-cell; ai.sp., attraction-sphere of germ-cell; bl.c, blood cell; bl.v., lumen of 

 blood vessel. 



3. Origin of the germ-cells 



Dantschakoff ('08) has described certain cells in the chick em- 

 bryo, which arise anterior and lateral to the primitive streak and 

 young embryo. The}^ originate, she states, from the margin of 

 the germ-wall entoderm. They begin to appear during the prim- 

 itive streak stage and continue to be produced until the embryo 

 has 3 pairs of somites. They are large, have a large round nu- 

 cleus and an abundance of yolk, and are especially character- 

 ized by their amoeboid properties. Because of their amoeboid 



