No. 3.] LATERAL LINE OF AMIA. 533 
of the supratemporal commissure, which is represented by a 
single whitish spot connected by a cord with the infra-orbital 
line. These two lines are short and indistinct. They lie be- 
hind the upper end of the opercular opening and immediately 
behind the slight prominence of the auditory vesicle. The 
middle dorsal pit line is represented by a large spot lying imme- 
diately superficial to the auditory vesicle, and connected by a 
faint cord with the line of the infra-orbital. 
Just in front of the auditory vesicle, the infra-orbital line runs 
across a depression, in the bottom of which, immediately below 
the line, is a dark spot marking the blind upper end of the 
spiracular canal. Above and in front of this point the line is 
enlarged; and from this enlargement organs 14, 15, and 16 arise. 
No opening into the spiracular canal could be found at this age 
or in one-day-old specimens. Behind and below the eye, the 
infra-orbital line is small; but in front of it, where organs 7 
and 6 arise, it is enlarged again. In front of this enlargement 
it again narrows; and the line of the anterior commissure is 
given off, the main line continuing on toward the nasal pit, 
and ending there in an enlargement which is indistinctly con- 
tinuous with the whitish border of the pit. 
The operculo-mandibular line is a slender and faint but con- 
tinuous line, lying along the anterior edge of a depression which 
marks the boundary between the operculum and branchiostegal 
rays on one side and the pre-operculum and mandible on the 
other. Its upper end lies in line with the spiracle, but is sepa- 
rated from it and from the infra-orbital by a strong prominence. 
A slight depression indicates the position of the horizontal 
cheek line, and another that of the vertical one. 
The raised whitish lines which in these early specimens rep- 
resent the growing sensory tissues disappear as the separate 
organs of the line develop, and there is left a slender white cord 
connecting them. This cord is doubtless the one found by 
Bodenstein in the adult of Cottus gobio (No. 3, p. 136), where 
it must be much more strongly developed than in Amia, for 
even in specimens only 40 millimetres long (or from twenty 
to thirty days old) it is traced with difficulty in sections. It 
is apparently the remnant of the cord along which the organs 
develop. In the four-day-old specimens, shown in Figs. 4 and 5, 
these cords are well defined, and most of the canal organs rec- 
