The germ-cells. 



653 



not noted in the present instance. The nuclei of some of the cells, 

 at any rate, exhibit a duplication. 



This mass of cells extends backwards under the head-region of 

 the future embryo. In doing this it lies almost directly under the 

 embryonic foundation, but more of it is massed to the right than to 

 the left. As will presently appear, its backward extension is for 

 some distance. 



The first germ-cell encountered within the embryonic foundation 

 is one in an abnormal position: it lies in the epiblast in the region, 

 just where the gut begins to fuse with the top of the yolk-mass. 

 Posterior to this the next one is a large one, like that marked Ä in 



C B 



text-figure A, and it lies at about the site of the future germinal nidus. 

 A dozen sections or so further back there is a large "megasphere" of 

 0.05 mm lodged in the foundation of the nervous system, and bulging 

 inwards from it. 



The gut-cavity is now open to the yolk, and there are still none 

 wandering into the embryonic foundation. In the fourth row of sec- 

 tions the mass of cells already referred to is still represented mainly 

 to the right of the embryonic foundation. The seventeenth section of 

 this row is that outlined in text-figure A. In the figure the boun- 

 daries of the various "layers" etc. are accurately depicted under low 

 magnification, and certain cells to the right of the embryonic foun- 

 dation are correctly represented by the black circles. For the sake 

 of simplicity only the cells to the right are included in the diagram. 



In the section of the embryo the following structures are seen: 



43* 



