The Germ-cells of Lophius. 573 



are diagrams prepared from sections through corresponding 

 parts of embryos of various ages. The general location of 

 germ-cells is marked by solid black circles. These figures do 

 not show the actual number or position of germ-cells in any 

 one section, but rather present a composite picture from several 

 sections. 



The youngest embryo in which I was able to recognize germ- 

 cells was of stage 6. At this time the blastoderm has not quite 

 half covered the yolk. Fig. 12 is an outline drawing of such an 

 embryo, and fig. 1 a cross-section. In this stage the ectoblast 

 is already considerably thickened but the thickening has not be- 

 come narrowed to form the well defined nerve cord of embryos 

 a little older. Below the ectoblast, lying upon the periblast, is 

 the primitive entoblast, made of rounded, loosely aggregated 

 cells, which show a rather indistinct arrangement in two layers, 

 the future mesoblast and entoblast (fig. 21). 



In embryo '6 F,' two germ-cells were observed, one at either 

 side, well toward the margin of the primitive entoblast, in posi- 

 tion indicated by the solid black circle to the extreme right of 

 fig. 1. Fig. 21 is a drawing of this cell and its surroundings. In 

 embryo '6 D,' just a little more advanced than the preceding, 

 there were observed two germ-cells, also in the entoblast, but near 

 the median line of the embryo (figs. 1, 12 and 22). In no other 

 embryos of this stage of development, was I able to recognize 

 germ-cells. Howev^er, in both of these embryos, as well as in 

 others of the same age, there were distinguishable quite a num- 

 ber of cells which may possibly be germ-cells that have not at- 

 •tained the characters which make them easily recognized from 

 this time on. The position of these cells is indicated by the open 

 circles in figs. 1 and 2. 



Embryo '6E' is somewhat more advanced than either of the 

 above. The entoblast and mesoblast are fairly distinct and the 

 notochord is separated. The mesoblast consists of about two 

 layers of cells; the entoblast of a single layer. The cells of both 

 of these germ layers are rounded and loosely aggregated. In this 

 embryo, seven germ-cells were distinguished, distributed in both 

 the entoblast and mesoblast (figs. 2 and 23). 



