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any marJced uniformity in the different embryos. A small proportion of the 

 embryos may show only the reddish-brown pigment cells with complete ab- 

 sence of melanaphores. Snch embryos are of a strikingly brilliant reddish- 

 brown color. '1 he 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, excejit 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 vei'y large, appear- 

 ing as a prominent bulb on either side. Tlie otoliths can be plainly seen. 

 I have seen no indication of a miiuth. 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 condition 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. 



