NOTES ON THE DEVELOPMENT OF THE NEWT. 577 
while still further back the closure of the neural canal is not 
yet complete. The neural ridge now extends through the 
head (fig. 16) and the anterior part of the trunk (fig. 13). 
It may be here stated briefly that, as far as our observations 
extend, the development of the spinal nerves is perfectly 
normal. The neural ridge is prolonged at regular intervals 
into nerves, which grow down between the medullary canal 
and muscle-plates. The upper part of each nerve developes a 
ganglion, and the ventral root is formed later, whether as an 
outgrowth from the medullary canal or from the ganglion we 
are unable to say. 
After our discovery of the neural ridge, we found that we 
had been so far anticipated by Bedot (5), who described in 
detail the development of the spinal nerves in the Newt. Our 
observations only confirm his on this point. 
The Cranial nerves, like the spinal, arise as paired lateral 
outgrowths of the neural ridge, being completely separate from 
the epiblast. Figs. 17, 18, and 19 illustrate those outgrowths, 
which give rise respectively to the 3rd, 5th, and 7th nerves. 
The 7th and 8th nerves are at first fused, and the common 
rudiment may be called, for convenience of description, the 
Facio-auditory nerve. 
The Trigeminal nerve (fig. 18) is an outgrowth from 
the dorsal surface of the brain, and is directed outwards and 
downwards towards a lateral thickening of the epiblast, which 
is cut transversely on one side of the section, and more 
obliquely, so as to appear longer, on the other side. 
The Facio-auditory has the same relations to the brain 
as the Trigeminal, and, like it, is directed outwards and 
downwards towards a lateral epiblastic thickening. The 9th 
nerve grows out similarly towards a corresponding epiblastic 
thickening. These thickenings are situated slightly above the 
level of the notochord, and are destined to give rise to the 
mucous canals of the head. It will be most convenient to 
take the future history of the nerves separately. 
The 3rd nerve is seen at a later stage in fig. 20. Its 
point of attachment has been shifted down the side of the 
