OBSERVATIONS ON THE CRANIAL NERVES OF SCYLLIUM, 477 
ganglionic roots are the new ones. We have studied these roots 
very carefully, but have been unable to determine with certainty 
whether they are outgrowths from the brain to meet the gan- 
glion, or from the ganglion towards the brain ;. our observations, 
however, though inconclusive, tend very strongly towards the 
latter of the two alternatives. It has also occurred to us that 
these new roots may possibly be the original primary root of 
origin (v a, fig. 1), which, after losing its original attachment, 
has acquired a new one lower down; however, though the dates 
of the disappearance of v a and appearance of v y agree fairly 
well with this hypothesis, we have yet no actual observations 
in its favour, and do not wish to lay stress upon it. 
These anterior roots which, during stage L, may be three or 
more in number, appear in the later stages to be very constantly 
reduced to two, one of which is the most anterior of the original 
roots while the other appears to be formed by the fusion of the 
intermediate ones. ‘This condition at stage N is well shown in 
fig. ll, vy. At a stage between o and P (fig. 14, v y) they 
are rather less conspicuous owing to the interval between them 
and the secondary root (v (3) being filled up by dense tissue. 
They are clearly recognisable in the adult, and form, as will be 
noticed more fully further on, the first or anterior root of the 
fifth nerve of zootomists. 
B. The branches of the fifth nerve-—The Gasserian ganglion 
is, from its first appearance, wedged in between the dorsal ends of 
the second and third head cavities in the same manner as is the 
ciliary ganglion between the first and second (fig. 11). From the 
Gasserian ganglion, at stage K, two nerves arise; of these, one, 
which runs straight down between the second and third head 
cavities, and then along the anterior border of the mandibular 
arch in front of the ventral portion of the cavity in the latter, 
is the mandibular branch, and from this, a considerable distance 
below the ganglion, a small anterior branch—the maxillary 
nerve—is given off. The second branch from the Gasserian 
ganglion arises from its anterior inferior angle, runs along the 
top of the first head cavity and joins the ciliary ganglion ; it is 
the communicating branch between the fifth and third nerves 
already mentioned, and forms the proximal part of the ramus 
ophthalmicus profundus of zootomists. 
At stage La slender branch arises from the anterior superior 
angle of the Gasserian ganglion; this is the ophthalmic branch 
of the fifth (fig. 10, v a) which runs forward through the orbit 
dorsad of all the eye muscles, giving off branches to the neigh- 
bouring parts in its course and terminating in the skin of the 
fore part of the head. One other nerve in connection with the 
fifth remains to be noticed: this is the connecting branch 
