354 JOHN BEARD, 



them. Then follow several simple fibrils on each side like those 

 already mentioned. Of these one is shown, after reconstruction, in 

 Fig. 28. The nerve is a process of a central ganglion-cell, its course 

 is along the outer side of the myotome, and there are three ganglion- 

 cells (gl.c^) applied along its lower border. 



From the following row of sections Fig. 30 is taken. Here a 

 similar nerve makes its exit from the summit of the cord, then, 

 becoming invested with ganglion-cells {w.gl.c), both above and below, 

 and arching over the myotome, in the succeeding sections its sub- 

 epiblastic course can be followed for some distance. The ganglion - 

 cells do not form merely a cover for the nerve, those nearest the 

 cord appear to be in connection with cells of the centre. 



A reconstruction of three sections not far in front of that shown 

 in Fig. 30 is afforded by Fig. 29. In or on the cord there are here 

 three ganglion-cells {gl c. c), one of which gives ofi a nerve-process 

 forming one element of the complex sub-epiblastic nerve (s.n) of the 

 figure. The rest of this nerve appears to owe its formation to the 

 nerve-processes of three ganglion-cells lying in the mesoderm, and the 

 nerve thus produced arches over the myotome and passes along its 

 outer side just beneath the epiblast. This is, however, not all. There 

 is also a ganglion-cell applied to the nerve as it nears the myotome, 

 and still another (w.gl.c) some distance along just beneath the epiblast. 

 The figure also reveals yet another ganglion-cell (glc^) lying in the 

 outer epithelium of the myotome. This latter cell is re-drawn under 

 higher magnification in Fig. 26. 



After the nerves of Fig. 30 there follow several simple "spun" 

 nerves in the same row of sections. One of these cases is worth 

 mentioning, because on the one side there is a nerve-fibre free from 

 ganglion-cells, while the corresponding nerve of the opposite side of 

 the body has a number of ganglion-cells applied to it. 



From this series there still remains Fig. 31 for description. Here 

 there is a ganglion-cell (w.gl.c) near the tip of the myotome. This 

 bipolar cell has nerve-processes extending in two directions. The 

 one passes over the tip of the myotome, whilst the other appears to 

 be really applied to a short process of one of the four central cells 

 (glc.c). It is only correct to speak of two processes for purposes 

 of description, for in reality the fibre appears to pass continuously 

 right along the ganglion-cell. For purposes of comparison a very 

 similar drawing from another embryo of 20 mm (Fig. 35) is placed 

 just beneath Fig. 31. 



