DEVELOPMENT AND LIFE HISTORY OF SOME TELEOSTS 
595 
Very soon after the embryo becomes well differentiated the purple spots become 
quite diffuse and shortly disappear. The pale, densely opaque center and the yellow 
spheres persist somewhat longer. At about this stage two black wavy lines or bars 
become evident on the yolk. These bars usually meet at one end in the form of 
a U or a V, although occasionally they are separate. The cellular structures on the 
yolk of the egg, mentioned previously, have become smaller and much less definite. 
About 48 hours (2 days) after fertilization at a water temperature of 26° to 
28° C. the embryo has nearly encircled the egg. Several somites are visible, but 
a definite count cannot be made. Circulation is evident. The heart is located 
under the anterior part of the head, from which a large blood vessel rises and courses 
through the length of the embryo to near the tip of the tail and then runs across 
the yolk back to the heart. If other blood vessels are present, they cannot be seen. 
The embryo already is capable of some movement. The black bars on the yolk, 
previously mentioned, are now broad and distinct and show indications of breaking 
up into spots in some specimens. The opaque center of the egg has disappeared, 
and very rarely a few spots, previously purple but now changed to pink, remain. 
In some eggs yellow spots are still definitely present. In others they seem to have 
become diffuse, giving the yolk a yellowish tinge (fig. 99). 
Figure 99. — Hypleurochilus geminatus. From egg with well- 
developed embryo; 2 days after fertilization. AV, auditory 
vesicle; H, heart; BV, blood vessels. Arrows indicate direc- 
tion of flow of blood. 
Figure 100 . — Hypleurochilus geminatus. From egg with mod- 
erately large embryo, encircling the egg; 3 days after 
fertilization. Note pigment on the eye and compare pigment 
on the yolk with that shown in figures 98, 99, and 101. 
About 72 hours (3 days) after fertilization, at a water temperature of 26° to 
28° C., the embryo slightly more than encircles the egg, although its entire outline 
generally cannot be seen. The eyes now are completely pigmented with black and 
overcast with green, particularly above the pupil. Circulation is brisk. The violet 
colors have entirely disappeared from the yolk, but a few yellow spheres still persist 
in some specimens. The two dark bars on the yolk usually are broken up into dark 
spots at this stage. Considerable variation in this respect, however, was noticed. 
The yolk has been reduced greatly and now occupies only about half the space within 
the egg case (fig. 100). 
Development progresses rather slowly in the advanced embryonic stages. About 
96 hours (4 days) after fertilization, at a water temperature of 26° to 28° C., the 
embryo has curved somewhat further round the periphery of the egg than in the last- 
