592 
BULLETIN OF THE BUREAU OF FISHERIES 
known, are guarded by a parent fish, it seems probable that they are similarly 
protected in the present species. 
DESCRIPTIONS OF THE EGG AND YOUNG 
Description oj the eggs . — Mature eggs within the ovary, according to preserved 
material examined, are slightly flat on one side to which a sort of disk, or “foot”, is 
attached. Immediately after spawning the eggs adhere firmly, by means of this 
disk, to objects (probably principally ascidians in nature) with which they come in 
contact. The disk as seen under the microscope in newly spawned eggs is granular, 
slightly irregular in shape, and a little greater in diameter than the egg. The eggs 
are relatively small, as the diameter of 25 ova secured from several different females 
(measured in the same plane as the surface to which they were attached) ranged from 
0.6 to 0.75 mm, with an average of 0.694 mm. 
The mature unfertilized egg is so opaque that its structure cannot be seen definitely. 
The center of the egg as seen with the microscope, using transmitted light, is somewhat 
paler in color and more densely opaque than the rest of the egg. The pale center 
is surrounded by purple and orange spots, or spheres, which vary among themselves 
Figure 91.— Hypleurochilus geminatus. From egg before fer- 
tilization. The adhesive foot is shown extending beyond the 
outline of the egg. 
Figure 92. — Hypleurochilus geminatus. From egg with blasto- 
disc, shortly before the first cleavage; about 25 minutes 
after fertilization. 
in the intensity of their color. By changing the focus of the microscope a slight 
network of cellular structures, too, is evident on the surface of the egg. The peri- 
vitelline space is very small and the yolk is slightly granular (fig. 91 ). 10 
Segmentation and the development oj the embryo . — Fertilization does not cause a 
change in the size and shape of the egg. The blastodisc becomes evident about 25 
to 35 minutes after fertilization at a water temperature of about 28° C. It is not a 
perfect disc, however, as it is somewhat irregular in shape and generally slightly 
elongate. Neither does it occupy the center of the upper surface of the egg. Owing 
to the density of the egg its outline usually cannot be seen definitely (fig. 92). 
The first cleavage occurs about 1% to 2 hours after fertilization at a water tem- 
perature of 27° to 28° C. The cells, wdiile notplainly visible throughout, appear unequal 
in size. Some variation in this respect, however, is evident. Upon completion of 
io Figures 89 to 102 were drawn from live material; those from 103 to 107 from preserved specimens. 
