The germ-cells. 645 



bring the total to 163. No germ-cells were noted in the segmented 

 mesoblast in this embryo. 



In this and the succeeding embryo the wandering cells (mega- 

 spheres) have not been counted, indeed, nothing in front of the pro- 

 nephros has been included. 



The distribution of the germ-cells in No. 441 will be commented 

 upon after the record of those found in No. 453. 



In the latter there were no germ-cells in the pronephric region, 

 in fact, there were none noted in front of the region of their greatest 

 aggregation. Here the germ-cells gradually increased as one passed 

 backwards; and, after culminating, they gradually tailed off, but ex- 

 tended almost to the cloaca. 



120 normally placed germ-cells were counted. There were 26 

 on the mesentery or splanchnopleure, only 5 within it, and 8 in 

 other places. Of these 5 were free in the coelom, one of them being 

 applied to the germinal nidus, and 2 were in degeneration. Another 

 one formed a simple "concentric corpuscle", one was in a nephridial 

 tubule, and the final one was in degeneration between splanchnopleure 

 and gut. 



The total is 159, almost the same as in the preceding embryo. 

 It should be mentioned, that here and there some of the sections 

 (usually single ones) are spoilt or deficient, and hence the count is 

 possibly not a perfectly accurate one. 



But the comparison of the two embryos is very interesting: 



Germ-cells R. hatis No. 441 R. hatis No. 453 

 Normally placed 126 120 



On mesentery 18 26 



In mesentery 8 " 5 



Elsewhere 11 8 



163 Ï59 



The table reveals a very striking resemblance between the two 

 embryos in the absolute number and in the distribution of their germ- 

 cells. This is partly accounted for, perhaps, by their similarity in 

 general characters and age; moreover, as already stated, they are 

 possibly sister-embryos ^). 



When compared with No. 454 (32 mm) or No. 488 (26 mm) the 

 following features are brought out. Relatively, the number of germ- 



1) More probably brother-embryos with maximum number of 

 255 germ-cells. 



