42 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
yolk diminishes rapidly in the yolk-sac, while in the elongated pouch along the 
ventral side of the alimentary canal no diminution is evident. On the contrary, there 
is an apparent increase; the entire yolk-sac becomes notably longer with the increase 
in the length of the body. Very soon (figs. 6 and 7) the oil-spheres, much elon- 
gated, with a small surrounding- 
mass, are all that remains as a 
spindle-shaped figure (fig. 6) in 
the yolk-sac. 
The yolk-sac does not at once 
lose its shape and bulk, but serves 
as an unusually large pericardial 
chamber which is equaled only in 
the practically yolkless Cymato - 
gaster. On August 5 the yolk 
along the alimentary canal had 
suffered little diminution, and its 
outlines were quite regular (figs. 
8 and 9). On August 6 this part 
of the yolk had become constricted 
in places, the outlines being less 
regular (fig. 10). The yolk had 
become yellowish in color and 
more fluid than vesicular. On the following day the constriction had deepened, and 
on August 11 the remains of the yolk were located in a series of minute globule 
more or less widely separated from each other. Long before this condition wa.- 
reached, about August 8, the larvae were taking food. 
The number of segments developed in front of the anus differs slightly, ranging 
from 65 to 71. The number beyond this point could not be determined exactly. The 
Fig. 6. — Head and anterior part of body, showing the continued reduc- 
tion of the yolk and the very large fourth ventricle. August 3. 
Fig. 7. — Outline of a larva somewhat older than that of fig. 6. 
notochord consists in its anterior fourth of single segments (fig. 11). In its middle; 
region the segments do not extend through its entire thickness, but in the tail it is 
again formed of single segments. The lines separating these are so much more 
conspicuous than the lines separating successive myotonies that it is impossible to 
