CRANIAL NERVES OF SIREN LACERTINA 285 
In Amphiuma the writer (’08, p. 537) described four groups of 
auditory fibers: 
(1) Medium and large fibers that pass posteriorly into the spinal 
VIII tract; (2) medium fibers that pass anteriorly into the so-called 
(incorrectly) ‘descending VIII’ tract; (3) medium and small fibers that 
pass into ‘tract b’; (4) large fibers forming a tract at first distinct from 
(1) but posteriorly passing into the spinal VIII tract or into very close 
proximity to it. 
In Necturus Kingsbury (I. c., p. 181) recognized three groups 
of fibers: two corresponding to (1) and (2) in Amphiuma and a 
third group ending almost immediately on entering the brain in 
close proximity to certain large cells. In Cryptobranchus Osborn 
(1. ec.) mentions four roots of the eighth nerve, but, as Kingsbury 
has pointed out, only one of these, VIII,” contains acoustic fibers, 
and is really the auditory nerve. 
In Siren the auditory nerve consists of two groups of fibers: 
(1) a large fibered anterior ventral tract turning posteriorly into 
the spinal VIII tract (figs. 21, 28-30, VIJIa.); (2) a tract of 
medium sized fibers, dorsal and posterior (VIII p.), which passes 
anteriorly within the brain (fig. 21). These two groups of fibers 
correspond to (1) and (2) in Amphiuma. A group of fibers 
passing into ‘tract’ b does not appear distinct from (2) in Siren. 
Group (4) of Amphiuma is evidently contained in (1) of Siren. 
2. The general cutaneous component of the facial nerve 
The presence of general cutaneous fibers in the seventh nerve 
of Amphibia has been commonly recognized, but no distinct root 
of the facialis entering the spinal V tract has been found. It is 
generally assumed by students of nerve components that any and 
all such fibers find their way into the seventh nerve from the tenth 
nerve through the ramus communicans cum faciali. To the 
writer’s knowledge no one has found general cutaneous fibers in 
the roots of the facial nerve. Any suggestion, therefore, of the 
occurrence of such fibers challenges contradiction and calls for 
a most critical examination of the so-called evidence. 
Driiner (’04, p. 661) has called attention to the small size of 
the ramus communicans in Siren. The writer has found in one 
