The germ-cells. 673 



peated itself here. It has been possible to establish the degeneration 

 and death of but a mere fraction of them. The cases figured are all 

 taken from a single embryo (No. 45-i), but, since they were drawn, 

 quite similar instances have been encountered in other embryos^). 

 They are not numerous, and, therefore, not easily observed. But at 

 certain periods of the development — in embryos of 25 to 40 mm, 

 if not in others — careful search will, as a rule, reveal the presence of 

 some of them. In No. 454 only some 8 germ-cells in undoubted 

 degeneration were encountered, and, so far as could be determined, 

 the remaining "lost germ-cells" exhibited no signs of atrophy or decay. 



In late embryos, in which all the organs are completed, that is 

 to say, at and beyond the critical period, no traces of the lost germ- 

 cells have yet met my eyes. It cannot for a moment be supposed, 

 that they ultimately find their way into the "germinal ridges". When 

 they have not reached the germinal nidus in embryos of 42 mm 

 (Nos. 628 and 642) it is hardly likely, that they will attain this in 

 still older embryos, where I have been unable to find them. By this 

 it is not intended to imply, that they certainly do not exist in these 

 latter. The quest is a difficult one, and it is not rendered easier by 

 the circumstance, that by this time they will have used up all their 

 yolk, the surest indication of their presence in earlier stages. The 

 remaining yolk is little enough in embryos of 42 mm (Fig. 12). 



What becomes of the lost germ-cells can only be surmised. Even 

 this may be left to the reader, who now knows as much about them 

 as the writer. But it does seem incredible, to suppose that 25^0 or 

 more of the original germ-cells should persist in abnormal situations ^). 



The few, whose degeneration has been closely followed, almost 

 without exception appear to have this character in common : they 

 were nearly all apparently freely roaming in the body-cavity. 



The changes about to be described seem to be capable of classi- 

 fication under two types. Each of them, however, is associated with 

 what Flemming^) has termed "chroraatolysis" — curiously enough in 

 a very similar connection. The figures illustrating the first of the two 

 types are Figs. 38 to 42, 44 and 45; and those of the second are 

 Figs. 43 and 46 to 48, all on Plate 44. The earhest phase met with 



1) And in other species, thus in Scyllium canicula and Pristiurus 

 melanostomus. 



2) In later phases many of them degenerate (Dec. 1901). 



3) Flemming, W., Ueber die Bildung von Richtungsfiguren in Sauge- 

 thiereiern beim Untergang GRAAp'scher Follikel, in : Arch. Anat. Physiol., 

 Anat., 1885, p. 221—244. 1. c. p. 223. 



