No. 3.] MUSCLES AND NERVES IN AMIA CALVA. 627 
having definite and constant relations to those canals or canal 
organs. The terminal buds are, on the contrary, found scat- 
tered irregularly over the external surface, mainly of the head 
and fins, and on the inner surface of the mouth and branchial 
cavities (No. 3). 
The canal organs and pit organs in Amia are all innervated 
by what are called the dorsal, suprabranchial, or lateral branches 
of the facialis, glossopharyngeus, and vagus nerves, and they all 
belong to what are called by Merkel nerve hillocks. In early 
stages of development they closely resemble each other (No. 3, 
p. 502), but in later stages they differ greatly, the pit organ 
retaining its embryological form and individuality, while the 
canal organ first increases greatly in size, and then, by the 
independent growth of other similar organs immediately adjoin- 
ing it, gives rise to a large sensory patch, or nerve ridge (Mer- 
kel), in which the separate organs lose to a greater or less extent 
their individuality. 
Portions of the canal lines in Amia are represented in cer- 
tain teleosts by lines of surface organs, and certain of the pit 
lines in Amia are apparently represented in certain teleosts 
and bony ganoids by canals containing organs. To the exam- 
ples already given of this in my earlier work (No. 3, pp. 471 
and 521) must probably be added the mucous canal at the base 
of the dorsal fin in Polypterus, mentioned, but not described, 
by Pollard in his work on the lateral line system in siluroids. 
He there states (No. 94, p. 545) that this canal is represented 
in Amia by the dorsal body line of pit organs. As I do not 
find a description of the canal and its innervation, I am unable 
to judge whether this be so or not. The canal may, however, 
be of the kind described by Emery as the accessory lateral 
lines of Fierasfer (No. 25, p. 209), and hence not comparable 
at all with the canals of the lateral line system as found in 
Amia and teleosts. As there is in Polypterus a supratemporal 
crosscommissure, the canal in question cannot be that canal, as 
is probably the case with the canal described by Pollard in the 
same place, that is along the base of the dorsal fin, in Clarias 
and Auchenapsis (No. 94, pp, 530 and 533). In these two 
fishes the innervation of the canal is given as by a great recur- 
