402 
BULLETIN OF THE BUREAU OF FISHERIES 
The mode of segmentation is quite usual for a teleost, and it does not differ 
noticeably from that described for the white perch ( Bairdiella chrysura) by Kuntz 
(1914, pp. 4 and 5). The blastodisc becomes somewhat elongate just before the first 
cleavage occurs, and then it is cut at right angles to the longer axis. (Fig. 17.) 
The second cleavage plane cuts the first at right angles. (Fig. 18.) This manner of 
cleavage continues as long as the process can be observed. 
The embryo shortly before it is released almost completely encircles the periphery 
of the egg. (Fig. 23.) The embryo is capable of considerable movement at this 
time, and the pulsation of the heart is clearly visible. Circulation of the blood, 
however, is not evident. Definite pigment spots are absent at this stage as already 
indicated, the auditory canals are plainly visible, the eyes appear to be extraordi- 
narily large, and the single big oil globule which remains unchanged throughout the 
incubation period and for some time afterwards, lies opposite the ventral surface of 
the head of the embryo. 
Newly hatched fish . — The newly hatched fish is only about 1.5 millimeters long. 
Its head is deflected rather prominently, and it contains a relatively large amount of 
yolk. The larva is quite helpless at this stage. It floats on its back, being capable 
of movement in this position only by the use of its free tail. Presumably, the larva 
is held in the position described — namely, with the ventral surface upward — by the 
yolk sac in which the large oil globule constantly occupies an anterior position within 
the sac. At hatching the larvae have a few greenish spots on the dorsal surface of 
the head and body, generally placed as follows: A few indistinct ones over the snout, 
a few larger and more evident ones 
just behind the head, a pair a short 
distance behind the auditory canals, 
another pair above the posterior part 
of the yolk sac, two over the vent, 
and two more at mid-caudal length. 
When the pigment spots are seen from 
certain angles they give the appear- 
ance of crossbars. The oil globule 
is slightly greenish in color. Occasionally it contains a few rather definite darker 
spots, but usually spots are missing. (Fig. 24.) 
Although the eggs of the pigfish and white perch are very similar, as already 
pointed out, the separation of the young is easy. In the pigfish the oil globule 
within the yolk sac lies near the head of the fish. In the white perch the oil globule 
lies near the posterior periphery 
of the yolk sac, far behind the 
head. Furthermore, at hatching 
nearly the entire fish, as well as 
the oil globule, in the white perch 
are dotted with greenish, granular 
markings, whereas these markings 
are missing in the pigfish and the color is as described in the foregoing paragraph. 
At a length of about 3.0 millimeters the white perch has become much deeper 
and stockier than the pigfish. Furthermore, the perch has a large amount of dark 
pigment on the body, especially over the abdominal mass, when preserved (color 
markings mostly greenish in life), whereas the pigfish at this size has no definite pig- 
Figure 24. — Orthopristis chrysopterus. Newly hatched larva with 
yolk sac. Actual length of fish, 1.5 millimeters 
