OBSERVATIONS ON THE CRANIAL NERVES OF CER- 
TAIN GANOIDS 
H. W. NORRIS 
The forms considered are Amia and Lepidosteus (Holostei), 
and Polyodon and Scaphirhynchus (Chondrostei). The cranial 
nerves of these forms bear very obvious relations to the degree 
of development of certain external sense organs. That Amia 
and Lepidosteus are teleost-like in their nerve relations accords 
with the common view of their relationships in general ; Polyodon 
and Scaphirhynchus on the other hand show in their cranial nerves 
elasmobranch relations. 
An outstanding feature of the nervous system of Amia is the 
presence in the skin of the head of an enormous number of 
“terminal buds.” These necessitate a correspondingly exaggerated 
nerve supply. The visceral sensory elements supplying these ex- 
ternally situated sense organs come from the facial, glossopharyn- 
geal and vagus nerves. To reach their destination in the skin 
these nerve fibers for the most part appropriate nerve trunks and 
branches already existing rather than develop new pathways. The 
ramus palatinus VII of Amia probably carries more of these 
taste-bud fibers to the skin than all' the other cranial nerves com- 
bined. But we know that the ramus palatinus is a visceral sen- 
sory nerve and ordinarily has no relations with the skin. In 
Amia the ramus palatinus reaches its cutaneous distribution 
through the mandibular and maxillary rami of the trigeminal 
nerve and the buccal, superficial ophthalmic and otic rami of the 
facial nerve. The supratemporal branches of the glossopharyn- 
geal and vagus nerves, usually lateral line exclusively, also carry 
taste-bud fibers. These latter branches anastomosing with the 
ramus oticus produce that which Allis calls a “closed circuit.” 
This condition in Amia can hardly be considered as primitive 
or typical, and the assumption that the trigeminal nerve funda- 
mentally contains visceral sensory fibers is unwarranted. 
In Lepidosteus there are fewer cutaneous taste-buds, conse- 
quently the ramus palatinus 'VII and other visceral sensory 
branches of the cranial nerves sending fibers to the skin are 
smaller. But the relations are fundamentally the same as in 
