640 ALLIS. [Vou. XII. 
in Auchenapsis the mandibularis facialis does not divide into 
an externus and an internus (No. 94, p. 533). 
If these several nerves are destined largely or entirely to the 
supply of terminal buds, as seems probable, the variation in 
their importance and position in different fishes is easily ex- 
plained, for the distribution of terminal buds and their number 
in any particular region varies continually. The nerves in 
Amia strongly indicate that in this variation certain of the 
terminal buds have wandered from the outer surface of the 
head into the mouth cavity. No other explanation can be 
given of the course and terminal distribution of the two inter- 
nal branches of the fourth branch of the maxillaris inferior 
trigemini. That sense organs can pass from the outer surface 
of the head to its inner surface is seen in the organ of the 
spiracular canal in Amia (No. 3, p. 501). Furthermore, Beard 
states (No. 10, p. 191, footnote 1) that he has evidence indicat- 
ing or proving that the end organs of taste arise from epl- 
blastic thickenings which have wandered through certain gill 
clefts into the buccal cavity. 
The two internal branches of the fourth branch of the maxil- 
laris inferior trigemini, in Amia, with or without the branches 
r.ghs and ght, seem to be represented in Protopterus by the 
inferior branch of the palatinus facialis, which Pinkus consid- 
ers the homologue of the chorda tympani (No. 89, p. 310). 
This inferior branch of the palatinus as a separate nerve is not 
found in Amia. In teleosts also it is not given by Stan- 
nius, but it is described by him in selachians. Van Wijhe 
does not give it in Acipenser or in the other ganoids described 
by him, but Collinge probably describes it, in Polyodon, as the 
mandibularis internus facialis, for that nerve, as shown in his 
Fig. 12, lies in front of the spiracle, and he says that it inner- 
vates ‘‘the primitive pores of the sides of the head and mouth”’ 
(No. 19, p. 518). It lies immediately in front of and closely 
accompanies the mandibular branch of the trigeminus which 
innervates “primitive pores” in the region of the maxilla. 
These two nerves if fused would seem to represent the maxil- 
laris inferior trigemini of Amia, provided the “ primitive pores ”’ 
described by Collinge are terminal buds or their derivatives. 
