OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM. 487 
ganglionic base, arises from the front part of the ganglion 
immediately below the root of the ophthalmic ; its deeper portion 
runs forwards and slightly downwards over the top of the third 
head cavity, and becomes connected with the main stem of the 
fifth ; it is referred to in the figures as V. c’. The more super- 
ficial portion passes on further forward in the same direction, 
crosses the mandibular arch, and enters the maxillary process, 
lying immediately superficial to the maxillary nerve, and just 
beneath the external epiblast ; it is referred to in the figures as 
vil d. 
(3) The third branch is the direct continuation of the main 
stem of the facial nerve; it runs downwards and backwards 
along the anterior border of the hyoidean arch, and is the rudi- — 
ment of the posterior or hyoidean branch of the seventh in the 
adult ; it is referred to in the figures as VII c. 
Of these branches the first, or ophthalmic, is from its earliest 
appearance connected with the dorsal or primary root of the 
seventh rather than with the ventral root. The second branch 
is the most remarkable of the three; its deeper portion forms, 
as we have seen, a direct connection between the fifth and 
seventh nerves, a communication which appears to be very early 
established, inasmuch as by stage x the connecting branch is 
already a nerve of considerable size; the superficial portion of 
this branch (vir @) is noteworthy, mainly on account of its very 
close relations with the maxillary division of the fifth nerve. 
At stage t the only changes of importance are, (1) that the 
several branches have increased in size, and, excepting the branch 
vit d, which has a very straight course, and ends abruptly in 
the skin, have divided into secondary branches near their termi- 
nations; and (2), that a small anterior branch has arisen from 
the hyoidean nerve (vit c), some distance from the brain, which 
runs forward over the top of the spiracular or hyomandibular 
cleft, and then down in the anterior wall of the spiracle, ¢. ¢. in 
the posterior portion of the mandibular arch; this branch will 
be referred to as vit 0. 
The several branches of the seventh nerve at stage N are well 
shown in the diagrammatic figures 1] and 12. The ophthalmic 
branch (vit a) is seen in fig. 12 arising from the base of the 
primary or dorsal root (vit a) as a stout nerve, which expands very 
shortly after its origin into a large somewhat fusiform ganglion, 
beyond which the nerve runs forward as a stout trunk to the 
extreme anterior part of the head. ‘Throughout its course it 
lies just beneath the external epiblast, and immediately dorsad of 
the ophthalmic branch of the fifth (v a), with which it is in very 
close relation ; like this latter nerve it gives off branches along 
its whole course to the integument of the neighbouring parts, 
