203 
stance. About midway along the lower surface of the nerve there is 
a large ganglion cell applied to the latter. From this cell an axis- 
cylinder process proceeds with the rest of the nerve to the myotome. 
Sectionsofthisstagearedecisiveinfavour of the func- 
tional activity of the apparatus; for the extreme dor- 
sal portion of the myotome, i.e. the region into which 
the nerve extends, contains a considerable deposit of 
muscle substance!). At certain stages it appears certain that 
this latter is no mere extension dorsalwards of the muscle innervated 
by any spinal nerve; for there is no continuity between the muscle 
of the apex and that lower down; or, in other words, there is a 
cellular region of the myotome between the two. 
Though the last figure (fig. 8) is taken from actual specimens it is 
somewhat diagrammatic. Intended to show a similar nerve to the one 
in fig. 7, it differs from the latter in that each axis-cylinder terminates 
peripherally, as in fig. 5, in a motorial end-plate, having the form of a 
ganglion cell (gl. ec’) lying within the myotome and embedded in muscle 
substance. It appeared likely that this interpretation of the peripheral 
ganglion cell, i.e. as a motorial end-plate, would be received with in- 
credulity. I was taught otherwise by more than one of my colleagues, 
who, on seeing the figure, at once suggested, without any hint on my 
part, that such must be the explanation. There need be, therefore, 
no feeling of reserve in enunciating this view, or in using such instances 
as evidence in support of the position I have long held, that motorial 
end-plates of muscle and the terminal plates of electric organs would 
appear to be really ganglionic in nature. 
The present communication has extended to an unwished-for length, 
although my notes on the apparatus have been merely dipped into, 
leaving much detail still untold. It may be of use to summarise the, 
present position of our knowledge of the transient nervous apparatus 
of a typical Vertebrate as follows: 
1) Except as above noticed, or hereinafter mentioned, the account 
given in my Lepidosteus note (1889) may still stand pro tanto. 
2) The apparatus of ganglion cells does not appear to extend 
quite to the extreme portion of the spinal cord. In Raja it certainly 
begins at about the 6% trunk somite (including the hypoglossus seg- 
ments), reaches a maximum in the region of the 11", maintains this 
with slight segmental variations until the 25 or 26 somite is 
1) In some embryos the apex of the myotome was seen to be forked 
when these nerves were distributed to the inner limb of the fork. 
