202 
VAN WYHE, and that he considered GEGENBAUR's (1871, 
p. 521) „ventral vagus roots”, the hypoglossus of other 
authors, (to which we will refer again in the second chapter), 
as belonging not to the vagus and to the head, but to the- 
spinal nerves. Thus BALFOUR believed that there were 
no ventral cranial nerves. 
VAN WYHE (1882, p. 40) points to another circumstance 
which may serve to account for the different character of 
the dorsal cranial and of the spinal nerves. BELL’s (1811) 
rule of the exclusively sensory character of the dorsal and 
the motor character of the ventral roots only applies to the 
striate, voluntary, musculature which is derived from the 
myotomes, and not for the smooth, visceral, musculature- 
which ows its origin to the lateral plate. While the former is 
innervated by the ventral spinal nerves, the latter is 
supplied by the sympathetic nervous system, the ganglia of 
which, as shown first by ONODY (1885), are separated onto- 
genetically from the primordial rudiments of the spinal 
ganglia, while moreover it has been shown that nerve 
fibres sometimes pass through the dorsal roots to the 
visceral muscles, as suggested already by VAN WYHE (1882, 
p. 41). Thus STEINACH (1895) demonstrated experimentally 
that in the frog the dorsal spinal roots contain motor fibres 
for the visceral musculature and the bladder. 
In the same way the motor portion of the cranial nerves 
does not supply muscles derived from myotomes, but the- 
primordial branchial muscles which, although being striate 
and voluntary, according to VAN WYHE must be numbered 
amongst the visceral muscles, since they are derived from 
the lateral plate. The difference between the cranial and 
the trunk nerves, then, is reduced to the separation of the 
sympathetic ganglia from the primary spinal ganglia in the 
trunk, while in the head this process is absent. Thus in 
a somewhat different manner we arrive again at BALFOUR's 
conclusion that the head in this respect exhibits more 
primitive features than the trunk, and that, returning to my 
theory, the dorsal cranial ganglia are more strictly homo- 
logous to the ventral ganglia of Annelids than are the spinal 
ganglia, from which the visceral ganglia have separated. 
Thus according to VAN WYHE the ancestral form of Chor- 
dates would have had not only dorsal roots of mixed 
function but, in addition to the latter, which only innervate 
the involuntary visceral musculature, ventral roots of purely 
