358 
any marked uniformity in the different embryos. A small proportion of the 
enibryos may show only the reddish-brown pigment cells with complete ab- 
sence of melanaphores. Such embryos are of a strikingly brilliant reddish- 
brown color. ‘The black pigment may be deposited in the eyes, however. 
The body of the embryo becomes considerably elongated, though never as 
long as the normals. The muscle segments are well developed; the vacu- 
olated notocord can be seen and the indications of the vertebral spines can 
in some cases be made out from a surface view. I have not seen the dorsal 
and caudal fin-folds developed, except in a very rudimentary way; the pec- 
torals, on the other hand, may be present, and in some embryos are larger 
than normal. The eyes are at first normally formed, showing as normal 
optic cups and a well developed lens, and having the normal size. Pigment 
begins to be deposited much as in the normal, but does not become as abun- 
dant. The eye does not keep pace. however, with the normals, so that it 
finally becomes too small, too slightly pigmented and often lying too low 
as well as too far forward. The ear vesicle may become very large, appear- 
ing as a prominent bulb on either side. The otoliths can be plainly seen. 
I have seen no indication ef «a mouth. The brain vesicles form in the 
earlier stage of the development of these hybrids. Later the brain shows 
cavities varying in size and regularity, but quite different from the normals. 
The peri-cardial cavity usually becomes quite large with a volume one- 
fourth or one-third the size of the whole yolk sphere. The heart becomes 
often much drawn out. In other cases it is relatively short and may show 
regions of differentiation. This pulsates vigorously, the wave going in the 
proper direction. I obtained a single embryo that succeeded in establishing 
a circulation so that blood was handled by the heart and circulated through 
the embryo and over the yolk. This circulation lasted for three days, when 
the vessels became clogged. ‘The heart continued, however, to beat without 
moving any blood. The usual condifion is to have no circulation established. 
Isolated regions on the yolk show capillaries with colored contents, but no 
movement of the latter obtains. In the embryo, likewise. lakelets of blood 
form. a favorite place being in the median ventral part of the tail just 
posterior to the yolk. I have kept embryos alive for twenty-nine days. 
The yolk may become reduced to one-half or more in amount. The embryo 
will not hatch. 
