528 ALLIS. [Vor. II. 
it is fully formed and before it has united with pore 17 operculo- 
mandibular, as shown in Fig. 13. In this case only the anterior 
one of the secondary pores takes part in the fusion with the 
opercular line. 
The canal of the lateral line, like the canals of the head, is 
first formed in short sections, which afterward become continu- 
ous. The rudiments of the different organs of the line are 
formed on the intermuscular septa, as described by Bodenstein 
and others in the bony fishes; but as the organ develops, it 
travels backward, and before being inclosed lies in the middle 
of the segment, as shown in Figs. 35 and 36, and as found by 
Malbranc in the Amphibia (No. 11). The organ then sinks 
into a little pit, and on its dorsal and ventral sides lips are 
formed which coalesce, forming a short canal about the length 
of a body segment, as seen in Figs. 36 and 37. The pri- 
mary pores formed by the union of the terminal openings of 
these short sections lie at first opposite the intermuscular septa 
and between consecutive scales, which at this age have only the 
length of a body segment and no free edge (Fig. 37, /p! and //’). 
As the scale grows its free hind edge pushes backward on 
either side of the primary tube and, uniting beyond it, leaves 
the pore on its outer surface (Fig. 38) and the tube at the point 
where the canal passes from one scale to the next (Fig. 48). 
The tube at first runs directly outward through the scale, but 
later it acquires a longitudinal position, extending backward 
almost as a prolongation of the short canal, and having on the 
outer surface of the scale one or more pores (Fig. 44). 
Toward the front of the head and along the mandibular line 
the canals are inclosed much earlier than in the parts behind 
the eye. The process in this part of the head is always greatly 
abbreviated after the manner detailed in describing the forma- 
tion of that part of the infra-orbital canal containing organs 15 
and 16. The development also proceeds so rapidly here that 
the canals in this anterior part of the system are fully formed 
before those behind it have much more than begun to develop. 
This anterior part includes the first six organs of the supra-orbi- 
tal line, the first ten of the infra-orbital, and the first nine of 
the operculo-mandibular. The canals inclosing these organs 
appear in specimens only five or six days old, and when the 
fish is from twelve to fifteen days old they are fully formed. 
