477 



do degenerate by one or other of two processes; these are simple 

 atrophy and the formation of cell-nests or "concentric corpuscles". 

 In both -'chromatolysis" is exhibited. But so far this degeneration has 

 been verified in but few of them, though it has been observed in 

 several embryos. One may surmise, that as a general rule the re- 

 maining vagrant germ-cells undergo a like fate. The writer cannot 

 believe, that the large number found on the mesentery in older em- 

 bryos (in no. 454 there where 110, in no. 448 even 120) will ever 

 find their way to the germinal nidus, or that they usually remain for 

 a long period unaltered in their abnormal situations. 



It is also recorded, that in Raja radiata no. 268, a young skate 

 and the equivalent of a R. batis of 70 mm, none were found on the 

 mesentery. It might repay the labour to study minutely phases from 

 45 to 70 mm or older. At the other end of the scale there is the 

 cleavage also clamouring for investigation. It is, indeed, the good and 

 the evil feature of a novel discovery, that it opens new fields and 

 raises new problems! The present writing does not exhaust the sub- 

 ject; although it may modestly claim to have thrown more light on 

 the early history of the germ-cells of Elasmobranchs than any previous 

 investigation. 



I confess that to me the importance of making out the degener- 

 ation of all the vagrant germ-cells appears very slight and unsub- 

 stantial, as compared with the overwhelming gravity of the incon- 

 testible discovery of a large percentage (28 to 30) of primary germ- 

 cells in abnormal situations in a vertebrate animal, and not in one 

 but in every individual under a certain age. Its bearings on patho- 

 logy, on Cohnheim's theory, and on the brilliant discoveries of Wilms 

 relating to dermoid cysts, must be apparent. The mere occurrence 

 of such vagrant germ-cells in all sorts of situations is sufficient. 



Whether or not they all usually ultimately degenerate does not 

 affect the application and import of the discovery. Even had the 

 degeneration of scores of them been witnessed, instead of a mere tithe, 

 the writer would still have felt bound to point out, that some of them 

 appear to be in positions as favourable for further persistence as in 

 the germinal nidus itself. As examples those frequently found on the 

 subintestinal vein may be cited. 



Doubtless, however, the pathologists will feel satisfied with the 

 discovery, that in a vertebrate animal 28 to 30 per cent of the primary 

 germ-cells are at certain periods in impossible situations. They will 

 not wish to assume, that as a general rule even one per cent of these 



