638 JOHN BEARD, 



close together. Correctness has been aimed at, and care taken, but 

 the result is given rather as an approximate estimate than as an 

 enumeration. 



In the rather wide sense indicated above there are 205 normally 

 placed germ-cells in this embryo. In No. 454 there were 349. The 

 difference might be accounted for by cell-divisions, but these cannot 

 be admitted. Though all three embryos, Nos. 402, 410 and 419, are 

 full of mitotic figures in other cells, not a single one has been met 

 with in a germ-cell. 



But now, what of the abnormally placed germ-cells? 



Confining our attention first of all to those in situations, similar 

 to the places noted in embryo No. 454, the resulting count does, in- 

 deed, give most remarkable figures. Figures they are, which almost 

 do away with the existence of abnormal germ-cells ! On the mesentery, 

 including the whole of the splanchnopleural covering of the gut, there 

 are in all — only 7 ! Of these 3 were close together in one section. 

 7 as against 110 in embryo No. 454! In other abnormal situations 

 there were again only 7, as against 45 in No. 454! 



The total of all the germ-cells so far recorded for embryo No. 410 

 is 219. In embryo No. 454 there were 512. Where are the odd 300 

 or so ? It cannot be supposed, that they are not yet in existence ^). 



Attention may be directed to the remarkable dearth of germ- 

 cells in the splanchnopleure, covering the gut and forming the mes- 

 entery. Here there are in all only 7, of which 3 are in a single 

 section. Their almost complete absence here is very significant. 



When one carefully studies skate-embryos of this period, it is 

 found, that many of the germ-cells, instead of reposing in abnormal 

 positions on the splanchnopleure, are underneath it. More, they are 

 in process of wandering upwards between it and the hypoblast. The 

 latter, it may be added, is still open to the yolk over a considerable 

 area. There is no figure in the plates of such a germ-cell from this 

 embryo. But Fig. 24 from a younger embryo may be taken as a 

 good example. (Compare also text-figure C, page 666, Fig. 7 A — D, and 

 Fig. 28.) 



It has been quite out of question to attempt to depict all such 

 sub-splanchnopleural germ-cells. In early embryos of 6 to 12 mm 



1) The supposition is, perhaps, easy, the proof of its correctness is, 

 however, impossible. From finds, made since writing the above, it is 

 probable, that embryo No. 410 was a potential male, the maximum 

 number of whose germ-cells would be 255. 



