626 ALLIS. [Vou. XII. 
arise, however, immediately behind the slight swelling of the 
tuberculum acusticum, and not from that swelling, as Strong 
states to be the case in all fishes (No. 121, p. 179). It runs 
almost directly backward, as described in my earlier work, an- 
astomoses with the root of the glossopharyngeus, as described 
above, and then continues backward, lying at a higher level 
than the ganglion on the posterior root of the acusticus, and 
at a lower level than the issuing roots of the vagus. On these 
latter roots an intracranial ganglion is formed, the root of the 
lateralis lying along its lower, outer surface. The lateralis 
then issues with the vagus through the vagus foramen, enters 
its ganglion and has the distribution already given (No. 3, 
p. 517). In the 14 mm. and 20 mm. larvae in which a ventral 
bundle of the root was found passing ventral to the root of the 
glossopharyngeus it could be distinguished as a separate bundle 
almost to the exit of the nerve through its foramen. 
7. Review and Comparison of Nerves. 
There are, as is well known, several kinds of more or less 
specialized sense-organs of ectodermal origin, found in greater 
or less number in all vertebrates. In the Ichthyopsida, where 
these organs are found in the greatest number and variety, the 
innervation of certain of them in certain forms is now definitely 
known, that of others is still largely unknown, as is also the 
development and interrelationships of all the organs. Some 
intimation of the relationships of certain of them can, however, 
be deduced from their innervation as already known, and the 
innervation, and hence relationship, of others is in a measure 
indicated by the relative size and extension of certain nerves, 
or their branches, in forms where certain of the organs undergo 
unusual development. 
In Amia three kinds or varieties of these organs are found, 
namely, canal organs, pit organs, and terminal buds, —the organs 
of the eye, the ear, and the nose being left out of consideration. 
The canal organs are always found, in the adult, inclosed in 
the canals of the lateral line system, and the pit organs at the 
bottom of slight pit-like depressions that are arranged in lines 

