MORPHOLOGICAL STUDIES. 
161 
matter have been “vollig unbeachtet,” and finds, — though 
this discovery is not likely to be accepted by anyone compe- 
tent to judge the question, — that his original views are 
practically identical with the generally accepted account of 
Balfour. 
Now, among those naturalists who have worked on the 
development of the peripheral nervous system, Balfour stands 
pre-eminent in the precise formulation of his conclusions. I 
am bound to maintain that on many of the most fundamental 
questions Balfour’s observations cannot be longer upheld, 
while I am also sure that none would be more ready than he 
to accept the facts I am about to record. 1 Balfour says (No. 
2, p. 369) : “ All the nerves are outgrowths of the central 
nervous system.” How this statement can be reconciled with 
his Zwischenriune hypothesis (for it is nothing more than an 
hypothesis) it is for Professor His to determine. The matter 
need not trouble us much, for, as I shall afterwards show, the 
Zwischenstrang (there is no Zwischenriune !) is just that portion 
of the epiblast or ectoderm which takes no part at all in the 
ganglionic formation. All I here wish to do is to enter a 
protest against the way in which Professor His attempts to 
convert all previous work on the early development of the 
ganglia into a mere confirmation of his own more or less 
1 It is certain that Balfour had an idea of the true facts, for he closes his 
account of the peripheral nerves on page 383 of the ‘ Comparative Embry- 
ology,’ vol. ii, with this passage : “ Situation of the dorsal roots of the 
cranial and spinal nerves. The probable explanation of the origin of nerves 
from the neural crest has already been briefly given. It is that the neural 
crest represents the original lateral borders of the nervous plate, and that, in 
the mechanical folding of the nervous plate to form the cerebrospinal canal, 
its two lateral borders have become approximated in the median dorsal line 
to form 1 lie neural crest. The subsequent shifting of the nerves I am unable 
to explain, and the meaning of the transient longitudinal commissure con- 
necting the nerves is also unknown. The folding of the neural plate must 
have extended to the region of the olfactory nerves, so that, as just stated, 
there would be no special probability of the olfactory nerves belonging to the 
same category as the other dorsal nerves, from the fact of their springing 
from the neural crest.” The reader may compare the first sentences of this 
passage with the results recorded in the following pages. 
