BRANOCHIAL SENSE ORGANS IN IOHTHYOPSIDA. 121 
ganglion along the snout and forms the supra-branchial branch, 
has just begun to develope. 
A glance at the diagrams (figs. 45 and 46) of the cranial 
nerves, according to the writer’s views, will simplify matters and 
pave the way for the account shortly to be given. 
Taking the ninth nerve, or glossopharyngeal, as a type of a 
cranial nerve to a true gill-cleft, we see that there is a main 
stem (p. 7.), a ganglion with associated sense organ, and then 
three other branches. These are—a post-branchial (p. n.), a 
pree-branchial (p. 6. n.), and a supra-branchial (s. 6. n.). As 
their names imply, the post-branchial and pre-branchial run 
behind and in front of the cleft respectively. The supra- 
branchial nerve is the nerve connected with the later developed 
additional branchial sense organs. 
Now we may turn to the nerve of the second segment. The 
first thing noticeable is that the cleft is absent,! or at 
any rate the gill muscles are not present even in the ontogeny. 
As a natural corollary to the absence or metamorphosis of 
the cleft, and absence of its muscles, the post-branchial 
and pre-branchial nerves are also aborted. 
In the diagram this abortion is represented by dotted lines 
(fig. 46). Hence all that we can expect to find of the posterior 
root of this segment is a supra-branchial branch to the branchial 
sense organs, the ganglion of the branchial sense organs, and 
the main stem connecting the ganglion with the brain. The 
ganglion is the ciliary, the main stem is the radix longa, con- 
necting the ciliary and Gasserian ganglia, and the supra- 
branchial branch is the ophthalmicus profundus. 
This identification is very similar to that given by Van 
Wijhe, but the matter is approached from an entirely different 
point of view. 
? Or metamorphosed. Dohrn has recognised what he believes to be a cleft 
behind the nose and in front of the mouth in the hypophysis. He does 
not say that it is the cleft of the ciliary ganglion, but this would seem to 
follow if Dohrn’s view were accepted. As at present, though possible, no 
relationship of this supposed cleft to the ciliary ganglion has yet been demon- 
strated, Dohrn’s view must be accepted with reserve. 
