59 
(oi) 
THE LATERAL CANAL SYSTEM. 
they are covered effectually directs the function downward through the 
opening at the lower edges. In some types the scale on which the disk is 
borne has become so enlarged as to lose its position and identity with others 
about it and to appear as if a superficial and accessory acquisition. There are 
such acquisitions outside of the disks, however, on Lamprogrammus. On 
the body of Phycis regius and on the top of the head of Halosauri the system 
appears to be more primitive in character than on other portions of the 
body. 
If in its inception the Lateral Canal System was tactile in function there is 
no evident reason why, in the complete darkness of the abysses, more than 
ever before demanding its exercise, this function should deteriorate or be 
lost; but instead all the circumstances would appear conducive to its en- 
hancement and perfection. Unless something better has been substituted 
for it, it is likely that the tactile function has been retained in the lateral sys- 
tems of all of the bathybial fishes. That the additional and very complex 
apparatus present on some species is to subserve the same purpose and 
nothing more is not so likely. Structure, pigmentation of adjacent tissue, 
apparatus for hiding effects or for controlling their directions, considered in 
connection with the absence or the presence of the eyes and their develop- 
ment, the character of the bathybial light and the probability of incursions 
into profound darkness all tend to make the conclusion unavoidable that the 
tactile organs of the lateral system have in the great depths become lumin- 
ous organs also, and that on many species they are so controlled by their 
possessors as to answer the purposes of flash organs. Again, the possession 
of apparatus in the disks beyond the needs of mere light organs, by blind as 
well as by eyed forms, indicates that there is yet more than the tactile and 
the luminous to be accounted for; and in these cases we are apparently 
driven to conclude that electric functions exist, functions by means of which 
the species or the sex of the individual is recognized, the members of the 
school are kept together, and by means of which the prey is captured and 
the enemy is avoided. A probable addition to the functions of the lateral 
system is the sense of taste; the sense of smell is otherwise provided for in 
well developed olfactories. 
In the Bulletin of the Museum of Comparative Zoology, 1888, Vol. XVII. 
p- 72, an attempt at the use of the lateral system in classification was made 
by the writer. In this essay special stress was laid upon the arrangement, 
connections, branching, ete., for the separation of species, genera and higher 
