The Development of the Cartilaginous Skull etc. in Necturus. 453 
The spinal ganglia usually lie at the side of the neural cord 
in early development. The ganglia of the first and second spinal 
nerves lie in the path of the motor nerve in Necturus, at some 
little distance from the spinal cord. This difference in position 
signifies perhaps little in itself, except that the space which the 
dorsal root must traverse in order to reach the spinal cord is con- 
siderable, and the root would consequently be less easily overlooked. 
I suspect, however, that FÜRBRINGER considers a ganglion and a 
dorsal root equivalent phenomena. The ganglia are there, but I 
have looked in vain for the dorsal roots of the first and second 
spinal nerves in Necturus. 
The ventral branch of the first hypoglossus nerve joins that of 
the second hypoglossus nerve, and for a short distance the nerves are 
united, after which the anterior branch extends forwards to supply the 
genio-hyoideus muscle, giving off branches also to the anterior part 
of its proper ventral muscle segment, which, in the posterior part, 
is supplied by the posterior hypoglossus nerve. The third spinal 
nerve, that of the sixth postotic segment, possesses a large ganglion 
with a dorsal root, and is the anterior nerve of the brachial plexus. 
The slender muscle omo-hyoideus, which secondarily separates 
from the anterior part of the ventral longitudinal muscle, belongs 
with the sterno- and genio-hyoideus to the ventral hypoglossus 
musculature. 
On page 454, a table is given, showing the relations of the 
segmental structures in the occipito-spinal region of Necturus in 
comparison with similar structures found in Petromyzon and 
Acanthias. Although the basis of comparison is the serial position 
of the organs, I would not thereby imply that a somite of Necturus 
is homologous with a somite of Acanthias or Petromyzon, merely 
because it occupies the same serial position. On the contrary, I am 
a believer in the view recently presented in the magnificent study 
of FURBRINGER (96, page 485), who reminds us, that »since the 
disappearance of occipital nerves from the head in Selachii, Ganoidei 
and Teleostei has been amply demonstrated, the postulate that nerves 
have been lost in the occipital region of the Amphibia, where 
even nerves that come through the free vertebrae degenerate, naturally 
suggests itself. On the ground that ontogenetic investigation has 
not as yet actually demonstrated the existence of such nerves, one 
is to a degree justified in assuming that in the Amphibia ontogeny 
gives a shortened recapitulation of phylogeny, so that these nerves, 
