236 JOURNAL OF COMPARATIVE NEUROLOGY. 
logically valid, and that too apart from the fact (of which he 
was aparently ignorant when he established the distinction) that 
the two types of organs are innervated by totally distinct nerve 
components, acustico-lateralis, on the one hand, and communis 
on the other. That neuromasts by reason of degenerescence, 
change of function, or some other cause, may sometimes sec- 
ondarly lose their pear cells is quite possible; but now that 
we know the innervation of these organs and have reason to 
believe that the nerve supply is invariable (i. e., that neuro- 
masts are always innervated by acustico-lateralis nerves and term- 
inal buds by communis nerves) it is possible to determine to 
which class any set of organs belongs independently of the 
presence or absence of pear cells, if only their innervation can 
be worked out. 
A comparison of the organs of the lateral line system of 
Ameiurus with those of other fishes shows clearly that the 
groups of naked neuromasts which I termed ‘‘pit lines’ in 
Menidia and Gadus correspond to the large pit organs of Amei- 
urus, and not to the small pit organs of this fish. It would ap- 
pear that those fishes do not posses anything comparable with 
the small pit organs described in the present contribution. Pos- 
sibly embryological study will shed some light upon the sig- 
nificance of the three types of neuromasts here described, and 
pending such an examination speculation upon these subjects 
may as well be deferred until we have more facts at command. 
ALLIS (’97, p. 629) mentions in Ameiurus catus the row 
of naked neuromasts across the tip of the snout and ‘‘two or 
possibly three lines on the top of the head.’”’ One of these is 
clearly the line continuing the supra-orbital canal caudal of its 
fifth pore of my account; the others are not described. He 
terms these organs ‘‘pit organs” but does not describe their 
structure. I find no evidence that he has ever seen the organs 
which I have termed small pit organs in this paper. 
