INVESTIGATIONS INTO THE HISTORY OF THE YOUNG SqUETEAGUE. 
51 
from pigment, but the cells are here smaller and contracted. A line of cells extends 
along the base of the anal and to the tail. The spinous dorsal is largely black; the 
soft dorsal and caudal have pigment cells along the membrane. All the chromato- 
phores at this stage are in the deeper layers of the dermis below the scales. 
With an increase of a few millimeters in length additional bands are interpolated 
between those mentioned, first one between the two under the soft dorsal, then 
one below the end of the soft dorsal, and lastly one between the two dorsals. All of 
these are formed by the time the fish has reached a length of 44 mm. to the base 
of the caudal. Eventually the deeper layer becomes deeply pigmented through the 
appearance of eh romatophores in the spaces between the bands. Numerous small 
chromatophores have also appeared in the superficial layer of the dermis, especially 
along the edge of the scales, so as to give a distinct black margin. With growth the 
chromatophores at the margin of the scales and those in the superficial layers of the 
dermis, as well as those on the fins, become very numerous. In specimens 75 mm. 
long to the base of caudal the bars are still faintly visible but the whole fish has 
taken on a dusky color on the sides, back, and fins, with a distinct black border to 
the dorsal and caudal. 
In a specimen 110 mm. long the black margins of the fins are less conspicuous, 
the black edge of the scales has become obscure on account of the great multiplication 
of superficial pigment cells. The bars of the young stage are entirely obliterated and 
the superficial pigment shows the characteristic oblique streaking of the adult, but 
much less conspicuously than in the adult. 
At this stage the color is due to the now uniform pigmentation of the deeper 
layers of the dermis blending with the streaked pigmentation of the superficial part 
of the dermis. With age the connective tissue between these two layers of pigment 
becomes so thick as to entirely eliminate the deeper pigment as a factor in the 
formation of the color pattern. The surface pigment, which is from the first laid 
down in streaks, alone gives value to the pattern in the adult. 
The obvious differences of the sexes appear so late that I can only report on the 
sex relations that no sex differences are apparent at a length of about 100 mm. 
