372 JOHN BEARD, 



10. Embryos of 10,5 cm. 



The body measures from the rostrum to the end of the pelvic 

 fins 3,5 cm, and the length of the tail is 7 cm. The greatest width 

 from side to side is 3 cm. There are long external gills. The 

 embryo is nearly seven months old. 



Sections have been figured from two such embryos, from embryo 

 No. 282, Figs. 109—111, plate 28, and Fig. 127, plate 29, and from 

 embryo No. 285, Figs. 108 a and b of plate 28. In embryo No. 282 

 the degenerating ganglion-cells are seen to be w^edged firmly into the 

 posterior fissure, which is now, as shown in Fig. 71 of plate 25, 

 about half formed. This wedging-in is very characteristic of Raja, 

 and has not been met with, at any rate in anything like this 

 exaggerated extent, in any of the other forms examined. It is the 

 direct cause of two things, one of which is a misfortune to the in- 

 vestigation of the degeneration of the transient ganglion-cells. This 

 latter is that, owing to it, it is difficult to make out much about the 

 poles and processes of the cells. The other of its results is a flat- 

 tening and squeezing of the cells until they have the tapering form 

 shown in Fig. 127. This varies in degree, and is not always met 

 with in so extreme a form. There is, however, one redeeming feature 

 about it. It proves that the cells, when degenerating, do not ofier 

 that resistance to alteration of shape which they are able to do in 

 the healthy condition ^). 



In Figs. 109 and 110 the shrivelled-up processes of the cells are 

 especially noticeable, the cell nucleus is elongated, with haematoxylin 

 it does not stain very deeply, and the nucleoli are fewer. A small 

 group of such degeueiating ganglion-cells as seen under high magni- 

 fication is represented in Fig. 127, plate 29. The irregular form of 

 the cell-body and the general decay of the nucleus and contents are 

 worthy of remark. Fig. Ill is intended to represent a degenerating 

 ganglion-cell in the muscle-substance of the myotome. When com- 

 pared with its central companions this cell is recognised as not more 

 degenerate than they. 



1) In a recent interesting publication M. Heidenhain remarks, 

 when referring to degenerating giant cells of the red marrow, that one 

 of the symptoms of degeneration of cells is their loss of resistance and 

 their becoming deformed by the lateral pressure of neighbouring cells, 

 — vide "Neue Untersuchungen über die Centralkörper etc.", in: Arch. 

 Mikrusk. Anat., V. 43, 1894, p. 630. 



