is | PROCEEDINGS OF THE NATIONAL MUSEUM. 169 
. They are surrounded by a thick zona which appears to be perforated 
Ks by two sets of canals, the usual fine canals and fewer much larger canals. 
_ In optical section these coarser canals appear as dark lines. The eggs 
_ readily adhere to each other, though they do not seem to possess the 
power of fastening themselves to foreign objects. When once fixed to 
each other they can scarcely be separated without injuring the zona. 
Ten hours after fertilization, eggs with one, two, four, and eight cells, 
respectively, were observed (Figs. 1-7). Thirteen hours after fertiliza- 
tion the most advanced eggs showed the sixteen-cell stage. The cells 
in this stage do not seem to be definitely arranged as in the eight-cell 
stage. Sixteen hours after fertilization the two layers of cells have 
been formed (Tig. 8). 
The blastoderm is completely segmented in thirty-five hours. At 
this time free nuclei are abundant. Stages immediately following are 
somewhat obscured by the opacity of the yolk. A well-advanced stage 
is represented by Fig. 9. The oil globules do not seem to have any 
definite relation to the blastoderm though they assume a more definite 
relation as soon as the embryo is outlined. At this stage they lie op- 
posite the middle of the embryo; as the embryo grows over the yolk 
they come to lie justin front of the snout. By the further reduction of 
the yolk the oil globules finally lie beneath and slightly behind the 
auditory capsule. The posterior end of the embryos figured (in Figs. 9 
and 10) terminates in a mass of large cells or rather small vesicles, the 
larger of which is situated below and may represent Kupffer’s vesicle, 
while after sixty hours the gastrula covers half the yolk, the blastopore 
is closed in some of the eggs after eighty-six hours. 
In the stage represented in Fig. 9 the yolk is covered by a network of 
fine lines which converge toward the tail of the embryo. 
On the fifth day the auditory capsule and the heart make their ap- 
pearance (Fig. 10). The heart lies somewhat to the left of the middle 
of the body. The body of the embryo at this time surrounds about 
half the yolk and the tail extends free one-third farther. The tail now 
lengthens rapidly, the pectoral fins being formed at the same time. 
The circulatory system is next outlined; it is from the beginning 
decidedly sinistral. The liver is at this time represented by a vascu- 
lar network overlying the yolk to the left of the embryo. The many 
vessels coming from the liver are collected in a large vein which at 
first is entirely on the left half of the yolk; at the time of hatching, 
however, it has been carried to the right side; with the reduction of 
the yolk this vein is greatly shortened in proportion to the veins empty- 
ing into it. 
The pigmented regions are outlined by the eleventh day. They are 
at this time distributed as they are when the yolk is almost absorbed. 
Round orange dots are also present at this time along the pigmented 
area, 
Peculiar granular cells or patches are formed about the head by the 
|| fourteenth day. These patches persist until the embryo is hatched 
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