No. 3.] CHEEK AND SNOUT OF AMIA CALVA. A441 
tral continuation of which nerve is said to be the mandibularis 
internus facialis. This latter nerve is said to innervate, among 
other organs, an inner row of mandibular sense organs lying 
along the margin of the lower lip. Another and more important 
row of mandibular organs is said to be innervated by the 
mandibularis facialis, this same nerve being later referred to 
as the external mandibular nerve (No. 29, pp. 531, 534). In 
Amia, both the preopercular and mandibular parts of the 
main line, and also the associated lines of pit organs, are all 
innervated by the mandibularis externus facialis alone, the man- 
dibularis internus facialis innervating no surface sense organs 
whatever, unless it be certain of the terminal buds (No. 3, 
p. 634). Confusion, therefore, at once arises, and to attempt to 
give definitely to these and other lines of sense organs, in fishes 
and other animals, the names of the nerves that innervate them 
before the homologies of the nerves and organs are well estab- 
lished, seems to me most unwise. Moreover, names based 
simply on the names of the nerves that innervate the different 
canals are not, in fishes, sufficiently definite tor detailed 
descriptions, and recourse must still be had to other terms. I, 
therefore, adhere for the present as closely as possible to the 
purely topographical method of naming adopted in my earlier 
work, using the innervation of the organs of the different 
parts of the system for comparative rather than descriptive 
purposes. 
Connected with the sense organs of the preopercular canal 
there is, in Amia, a horizontal line of pit organs, above 
referred to, which extends across the cheek from among those 
surface openings of the dendritic systems of the preoperculo- 
mandibular line that form groups 14 and 15 of my descriptions 
to those that form group 12 infraorbital (No. 1, p. 506). In 
four-day-old specimens this line is almost a direct continuation 
of a dorsal part of the preopercular canal line, that part of the 
canal line being distinctly separate from the ventral part (No. 
I, p. 534, Fig. 2). In part of its course this line of organs lies 
directly superficial to the lower postorbital bone. In Esox the 
corresponding line has moved bodily forward, ventral to the line 
of the suborbital lateral canal, and lies superficial to the lachry- 
