INFLUENCE OF LATERAL-LINE CANALS 323 
a graded series of specimens ranging in length from 12 mm. to 
60 mm. The desired stages were found between 18 mm. and 
35 mm. This having been determined, the necessary stages 
were set aside for sectioning, and study of the cleared specimens 
began. 
Since the results of this study are rather complex, being an 
attempt to correlate the facts of development, adult anatomy, 
and paleontology, the following account is divided into, 1) actual 
observations on Amiurus, 2) suggested explanations of osteogene- 
sis, and, 3) their application to paleontology. 
THE BODY CANALS 
While my study is chiefly restricted to a determination of the 
conditions in the head, yet it will be of great importance to 
state that the body lateral-line canals are often, in fact, usually, 
associated with dense connective tissue which may become ossi- 
fied. The association of the sense organs of the skin of the body 
with dense connective tissue in Amiurus is shown in figure 5. 
The canals, though frequently composed of dense connective 
tissue (fig. 5, c.t.) or cartilages, are often highly differentiated 
and are referred to as ‘drain-pipe bones,’ a term applied to the 
suborbital chain of bones in the head. Wright (’84, p. 263) 
has given an interesting account of the histology of the body 
canals of Amiurus, contrasting them with the lateral-line canals 
of the head (ibid., p. 264). The condition of the sense organs 
in relation to the cartilage of the body canals has been described 
by Latimer for Polyodon (719) and by many other writers for 
various fishes. What influence the lateral-line sense organs 
have upon the development of the heavy material of the body 
canals has never been determined, so far as I am aware, and 
since it is outside the scope of this investigation it must be left 
for future study. 
NATURE OF THE HEAD SKELETON OF AMIURUS 
It was quite evident from an examination of specimens of 
about 20 mm. in length that there were two or more sets of bones 
in the head of this animal, as had already been suggested by the 
work of Schleip and Klaatsch in other fishes. 
THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 34, NO. 3 
