536 ALLIS. [VoL. II. 
5. Organs 19 and 18 infra-orbital, the three organs of the 
supratemporal cross-commissure, and those of the posterior 
dorsal pit line, all innervated by a dorsal nerve arising from the 
ganglion or root of the WV. /¢xe@e lateralis. 
6. The organs of the lateral line of the body, organs 20 and 
21 infra-orbital, and those of the accessory lateral and dorsal 
pit lines of the body, all innervated by branches of the V. linee 
lateralts. 
All these organs in the early stages of their development lie 
below the surface, but they soon push through the overlying 
epidermal cells, and their upper central portions become exposed. 
Each pit organ subsequently sinks slightly below the surface, 
and a little epidermal pit is formed above its central portion. 
The canal organs also sink below the surface, but they carry 
with them the surrounding tissues and by a process of infolding 
become inclosed in short canals, each containing a single organ. 
These short canals then become continuous, a single surface 
opening being left between every two consecutive organs along 
each line. These simple openings, or primary pores, may be 
retained in the adult, but most of them undergo a repeated 
dichotomous division, thus giving rise to groups of surface pores 
and to corresponding dendritic systems of canals. 
By the union of the primary groups of short canals three 
principal canals are formed and two cross-commissures ; namely, 
the infra-orbital or main canal, which is continuous with the 
canal of the lateral line of the body, the supra-orbital and 
operculo-mandibular canals, and the anterior and supratemporal 
cross-commissures. The anterior commissure has, following 
the terminology of other writers, been considered as a part of 
the infra-orbital canal. It lies over the snout, and connects the 
infra-orbital lines between organs 5 and 6, which are properly 
the first two organs of the line. The supratemporal commis- 
sure lies in the temporal region, and connects the main lines 
between organs 18 and 19, or directly opposite organ 18. The 
supra-orbital and operculo-mandibular canals have no connection 
with the corresponding canals of the opposite side. They arise as 
independent canals, but the supra-orbital, soon after its regular 
formation, anastomoses between organs 6 and 7 with the main 
canal between organs 14 and 15; and the operculo-mandibular, 
by its terminal opening, with the main canal between organs 
