376 JOHN BEARD, 



Figs. 126 and 130 are from sections of the anterior trunk region 

 of this embryo. 



The degeneration has probably nearly reached its termination. 

 Indeed, in this and the following embryo the remains of the cells are 

 much more rarely encountered in sections. When one does meet 

 with them, they are, as in Figs. 126 and 130, small shapeless particles, 

 often fissured, and possess only the faintest traces of a nucleus. 

 This latter now appears to be absolutely indifferent to staining reagents. 



16. Recently hatched embryos. 



Three embryos were brought to this stage. They had probably 

 been hatched some days before the circumstance was noted. The 

 measurements vary somewhat in the three specimens; from the snout 

 to the end of the pelvic fins is from 10 — 13 cm, the tail from 9,2 — 9,5 cm, 

 and across the paired fins from side to side , at their widest part, 

 12—13 cm. The age is from 17—18 months. 



The remains of the cells are now difficult to find. What is left 

 of a single cell may be encountered in one out of fifty thick 

 sections, and this in that region where the ganglion-cells were for- 

 merly very abundant. 



In Fig. 131 a— d will be found such examples of the progress of 

 the degeneration as could be detected in some 200 sections of embryo' 

 No. 375. 



The cells, if one may still call them by this name, are withered 

 and contorted almost beyond recognition. Little of the nucleus is to 

 be seen, often nothing at all. This is the furthest limit to which they 

 have been followed. Young skate for a stage further might possibly 

 have been obtained, but there would have been profitless labour in 

 further prosecution of their career, which, where they still exist, is 

 closing, or already almost finished. It would have been wearisome to 

 have gone thus far into the matter, but for the fascination and charm 

 these cells and their problems exerted. In a few pages the results 

 of investigations into the degeneration have been briefly recorded — 

 of investigations which entailed months and months of labour. Time 

 has been sacrificed which might have been saved, but for the desire 

 to give as complete and true a history of these ganglion-cells as 

 possible. 



Should anything be wanting in the continuity of the demonstration, 

 the material may be blamed rather than the writer; for even a 

 "perfect" set of stages of the embryology of a form can never quite 



