332 JOURNAL OF COMPARATIVE NEUROLOGY. 
The question seems to me to involve the correctness of the 
interpretation of the chorda tympani as pretrematic, and the 
homology of the mandibularis internus VII, in Menidia, Amia 
and Selachia, which appears to have a course somewhat different 
from that of the branch in Urodeles. For a comparison of the 
relations in fishes and Amphibia, the effect of the morpholog- 
ical differences in the suspension of the jaw and the value of 
the relation of nerves to skeletal structures in determining their 
homology, are involved; and for the larger question of the 
chorda tympani, the homology of the sound-transmitting appa- 
ratus in the different classes, as well; so that it seems to mea 
close consideration of homologies is yet premature. 
The pre- or post-trematic origin of the R. mandibularis 
internus in Urodeles cannot, of course, be determined, since 
the first gill cleft does not come to development. From its 
point of origin and course, it certainly could be pretrematic, as 
Coxe’ has pointed out, and it seems to me the possibility that 
this nerve represents a pre-trematic nerve such as GREEN, 
(e. g.) described in Selachia,? is worth considering. In this 
connection the different relations of the facial nerve and col- 
umella auris in Anura and Urodela must also be considered. 
There is here presented in allied forms, a difference of relation 
1°96, CoLE, F. J. On the Cranial Nerves of Chimaera monstrosa (Linn) 
with a Discussion of the Lateral Line System and of the Morphology of the 
Chorda Tympani. 7Zyvamns. Roy Soc., Edinburgh, Vol. XX XVIII, Pt. II, 
(No, 19). 
21 have already referred to the statement by COGHILL (p. 228) that this 
nerve could be considered pre-trematic. In the forms studied by me, however, 
the conditions, I believe, hardly warrant a definite conclusion. COGHILL, 
even, would regard the R. mandibularis internus in Urodela and Anura, as not 
homologous (p. 265), and this, too, seems to me rather extreme. The entire 
hyomandibular nerve in the frog crosses over and behind the columella auris 
and in Urodela under and in front of it. As stated in a previous paper (’95, 
The Structure and Morphology of the Oblongata in Fishes; Journ. Comb. 
Neurol., Vol. VII, p. 30) where I quote also the opinion of Miss PLATT to that 
effect, I feel that the origin and distribution of a nerve are of more importance 
than its course, which may vary, and consequently should not be too closely 
made the basis of homologies. We also see that the relation of a nerve to a 
muscle cannot be relied upon as a test. 
