494, PROF, MILNES MARSHALL AND W. B. SPENCER. 
Gegenbaur speak of the ophthalmics as rami dorsales, but refer 
them entirely to the fifth. 
What the causes are which have led to the very marked 
extension forwards of the rami dorsales of these nerves is not 
very evident ; we would suggest that it is due mainly to an 
extension forwards and accumulation at the anterior end of the 
head of the special tegumentary sense organs—the mucous 
canals—this extension forwards involving a corresponding exten- 
sion of the nerves supplying these organs; in connection with 
this suggestion it is of interest to note that no one of the nerves 
in front of the fifth sends any branches to these organs. Whether 
there is any trace of a ramus dorsalis to the third is very doubt- 
ful; at any rate the fourth nerve cannot be the ramus dorsalis 
of the third, as its course is, at first, at right angles (fig. 11) to 
the rami dorsales of the fifth and seventh nerves; and, secondly, 
it is a motor and not a sensory nerve. 
We now come to a far more intricate problem, viz. the import 
of the connecting branches between the third, fifth, and seventh 
nerves, with which it will be convenient to consider the nerve J. 
(figs. 10, 11, 12, and 15). 
These three nerves, VV. c., V.c.’ and WV. all appear very early ; we 
have failed to determine the date of their first origin, but by 
stage K they are fully established. The posterior one (J. ¢’.), 
connecting the fifth and seventh nerves together, is the most 
difficult to investigate, owing to its appearing from the first as 
merely the deeper portion of the buccal nerve (fig. 6); in longi- 
tudinal sections, however, it appears very distinct (vde fig. 10). 
It is from the first much shorter than either of the other two 
nerves we are considering, and in the later stages (fig. 14) and 
the adult condition, owing to the close approximation of the fifth 
and seventh nerves, ceases to be visible as a distinct trunk. 
The second of the three nerves (J. c., figs. 10 and 11) forms, as 
already noticed, a direct connection between the Gasserian gan- 
glion of the fifth and the ciliary ganglion (c.g.) of the third 
nerve, and is much more slender than WV. c’. Concerning the 
nerve in question, it is of the utmost importance to notice that not 
only is it fully established at the stage at which our observations 
commence, but that it is from the very first a connecting nerve, 
and that there is no reason whatever in the early stages for con- 
sidering it as belonging to the fifth rather than to the third nerve. 
We have, therefore, in this paper given it a perfectly neutral 
name, 
The last of these nerves, W., is still more remarkable; like the 
others it is present at K. Starting at this stage from the ciliary 
ganglion it runs an almost perfectly straight course to the anterior 
