No. 3.] LATERAL LINE OF AMIA. 523 
correspondence of each scale of the lateral line in Amia to a 
segment of the body, and has suggested the possibility of some 
sort of relation between the dermal bones of the head and the 
cranial segments. The arrangement of the sense-organs and 
nerves of the lateral system, the regular occurrence of primary 
tubes between consecutive dermal bones of the head, as well 
as between consecutive scales of the lateral line, and the singu- 
lar correspondence between the infra-orbital and opercular canals 
is further evidence in this same direction. 
Hi eLARVAL FORMS. 
1. Formation of the Canals. 
The inclosing of the lateral canals and the formation of the 
ninety-three normal primary pores and tubes is essentially a 
simple and regular process, but in most parts of the head marked 
abbreviations take place, which greatly obscure it. Where the 
process is regularly and fully carried out, the canals arise in 
separate sections, each of which contains a single sense-organ, 
and hence corresponds to the part between two primary tubes 
in the developed canal. This has already been described by 
Bodenstein in the lateral line of Cottus (No. 3, p. 142) and 
by both Schulze (No. 16, p. 69) and Solger (No. 18, p. 386) in 
Plateria. 
If young Amia, in which the canals have not yet begun to 
develop, are hardened in chromic or picro-sulphuric acid, the 
organs of the lateral system, still below the surface, appear as 
whitish spots, with indistinct outlines, strung along more or 
less continuous whitish lines. These lines mark general and 
extensive surface depressions. After a developing canal organ 
has reached the surface at the bottom of one of these depres- 
sions, it begins to sink, carrying with it the surrounding tissues, 
thus forming a small pit, at the bottom of which the organ lies. 
A series of changes now begin, which, on an exaggerated scale, 
are a repetition of those which lead to the division of a pore. 
Lips grow upward and inward from the edges of the pit, and, 
meeting above the organ, form a short section of canal, the 
openings of which are inclined to the general surface, and give 
to the canal a tunnel-like appearance. A narrow shallow chan- 
nel, pigmented like the rest of the outer surface, has meantime 
