1891.] The Genesis of the Chromatophores in Fishes. 113 
the time of hatching, when bright yellow pigment appears. In 
the pelagic ova observed, excepting Stolephorus, black pigment 
was always formed, but never in great quantity. In Serranus 
nebulifer (Fig. 34) only black pigment is formed before hatching, 
while in Serranus maculofasciatus, Sciena saturna, and Hypsopsetta 
guttulata the few black cells are almost obscured by the great 
number of brownish-yellow cells. In those cases in which both 
black and yellow cells appear the black cells soon collect on the 
lower surface of the oil-globule and on the lower surface or back 
of the embryo, while the yellow cells are aggregated on top of the 
oil-sphere and on the ventral surface of the embryo,—a fact 
already observed by others. 
Figs. 32 to 41 will give a fair idea of some of the various 
patterns the color-cells form in early stages. ‘Figs. 33 to 40 rep- 
resent nearly homologous stages of various embryos. The time 
required to reach thése stages differs, however, vary greatly in 
the various species. Figs. 33, 34, and 40 represent larve between 
two and three days old, while Figs. 35 to 39 represent larve as 
many, or more, weeks old. The conditions of development also 
vary greatly in the larve selected for illustration. Figs. 33, 34, 
and 40 are all hatched from pelagic ova ; Fig. 36 from ova which 
adhere together and are thus hatched in masses; Fig. 38 from 
ova with a mycropylar circlet of filaments; and Fig. 39 from 
ova with isolated filaments scattered over the entire zona; while 
Fig. 37 represents a viviparous fish just at the time of birth. 
Viviparity does not affect the chromatophores immediately. 
In the rock cod (Sebastodes), Fig. 37, color is as well formed at 
the time of parturition as in some related viviparous species. In 
the Holconotidz, on the other hand, color is not formed until 
quite late stages are reached, and the eyes are the first to be 
pigmented. . 
. In all cases observed the chromatoblasts originate in the meso- 
blast surrounding the embryo. This condition was considerably 
modified in Scigna saturna, in which they are formed along the 
entire margin of the embryonic ring ; but the difference is one of 
degree only. 
