GANGLIA AND NERVES OF SQUALUS 27 
lateral to the point of contact of the root of the profundus with 
the Gasserian. From its point of exit it pursues a course ceph- 
alad parallel to the longitudinal axis of the body and slightly 
ventral and mesial to the r. oph. sup. VII and parallel with that 
nerve to a point approximately over the anterior end of the 
lens, where it comes into-contact with the superior oblique muscle 
of the eye. This contact is at the point of entrance of the 
trochlear nerve into this muscle and the sensory nerve could 
not be traced beyond this point in the specimen plotted, conse- 
quently no mass of cells at the growing point of the nerve could 
be identified such as Neal (14, plate 7, figs. 55 and 56) figures. © 
There is, however, a mass of cells apparently not belonging 
to the muscle but slightly detached from it and containing a 
few large cells which may be the mass figured by Neal but 
seems rather to be the primordium of the sympathetic ganglion. 
This nerve is evidently in a much less mature condition than in 
the 25 mm. specimen figured by Neal. It may be mentioned 
incidentally that in my specimen the trochlearis does not show 
the two well defined rami which he figures in plate 7, figures 
54 and 55. These two terminal rami in the specimen plotted 
are quite small. Otherwise my findings agree with those of 
Neal and I have nothing to add to his very thorough descrip- 
tion of the eye muscle nerves. Ther. oph. sup. V gives off one 
small twig about the middle of its course which runs close to the 
ectoderm but could not be traced into it with certainty. There 
is, of course, owing to the small size of this ramus no anasto- 
mosis with r. oph. sup. VII, as in the adult. 
The small size of the r. oph. sup. V in Squalus as compared 
with the large r. oph. prof. at this stage furnishes a basis for an 
interesting phylogenetic comparison of these nerves, in embryos 
of different types. In Lepidosteus at approximately the same 
stage (Landacre, ’12, fig. 1) the two nerves are equal in size. 
In embryos of urodeles (Coghill, ’16, figs. 1 to 4), the ophthal- 
mic ramus comes from the profundus ganglion and is identified 
by him as r. oph. prof. In Anura (Landacre and McLellan, 
12) only one ophthalmic ramus comes from V and this comes 
from the profundus portion of the fused profundus and Gasseri- 
