608 
BULLETIN OF THE BUREAU OF FISHERIES 
The eggs in which cleavage started at about 10:30 in the morning reached a fairly- 
advanced cleavage stage by the evening of the same day (fig. 116). The temperature 
of the water had remained near 26° C. throughout the period. No pronounced 
changes had taken place in the egg in the meantime, except that the yolk apparently 
had become more granular and rather more opaque. 
Twenty-four hours after cleavage started a very early embryonic stage was 
reached, that is, the embryo was just becoming differentiated, though it was not yet 
possible to distinguish between the head and tail. The temperature of the water had 
dropped to 24.5° C. Little obvious headway was made during the next 12 hours. 
However, a fairly well-formed embryo, with the eyes partly developed, was present, 
at about 48 hours after fertilization. The temperature of the water had advanced to 
26° C. The embryos evidently were not all in the same position in relation to the 
adhesive foot. In some eggs the embryo lay underneath the yolk, next to the foot, 
with only the head and tail visible if viewed from the side opposite the foot. Other 
embryos lay mostly above the yolk and therefore were entirely visible in eggs seen from 
the same angle. Positions intermediate of these also were observed. A few grayish 
blotches, variable in size, were noticed on the yolk for the first time (fig. 117). 
About 60 hours (2 % days) after fertilization, the temperature of the water remain- 
ing near 26° C., the embryo was well formed, with a large head and partly pigmented 
eyes. It curved about two-thirds the distance around the egg. Indications of 
somites were present at midbody length and the heart beat slowly and rather feebly 
(about 90 beats per minute). Circulation was evident only near the heart, no definite 
blood vessels apparently having been formed. Black blotches, with irregular outlines, 
variable in size and shape in any one egg and variable in number in different eggs were 
present on the surface of the yolk (fig. 118). 
On the fourth day of incubation, with the temperature of the water remaining 
quite constant at 26° C., the body segments had become plainly marked in the anterior 
caudal region, although the embryo had gained little in length. The eyes had many 
black pigment dots, most numerous along the upper margin ; the yolk appeared very 
granular and had been cut into deeply by the embryo, and the dark spots on its surface 
Figure 117 —Chasmodes bosquianus. From egg with moder- 
ately well-differentiated embryo; 2 days after fertilization. 
(Drawn by Nell Henry.) 
Figure 118.— Chasmodes bosquianus. From egg with well- 
formed embryo; 2Yi days after fertilization. Tail of embryo 
curved under the opaque yolk. (Drawn by Nell Henry.) 
