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CHARLES H. SWIFT 



germ-cells cytologically are very similar to the cells of the germ- 

 wall near its border (fig. 14) ; mitoses are also seen in these cells 

 (fig. 14). 



When the mesoderm reaches this region anterior to the embryo, 

 which it does relatively late, the germ-cells enter the mesoderm 

 and the forming blood-vessels. 



\ •••• 



Fig. 14 Portion of a transverse section through an embryo of primitive streak 

 stage development. ]\Ieves' fixation andMeves' iron-hematoxylin stain. X 1125. 

 pr.o., primordial germ-cell; a., cell of germ-wall, which resembles primordial 

 germ-cell; a'., cell of germ-wall dividing; at.sp., attraction-sphere of germ-wall 

 cell; g.w., germ-wall entoderm; ect., ectoderm. 



As regards the history of the entodermal wander-cells in the 

 blood there is also a close agreement with that of the germ-cells. 

 However, a majority of the germ-cells do not degenerate in the 

 blood stream or in the tissues. Only a few of the germ-cells 

 leave the vessels before a stage of 21 somites is reached and only 

 a few degenerate. 



