BULLETIN OF THE UNITED STATES FISH COMMISSION. 187 



serous space, unless by a purely physical process of transudation, or 

 osmosis of water from without, which keeps pace with the collapse of 

 the yelk, the absorbed water taking the place of the latter as it dimin- 

 ishes iu volume? 



II. — NOTICE OF AN EXTRAORDINARY HYBRID BETWEEN THE SHAD 



AND STRIPED BASS. 



A number of young fish which had already lost their yelk sacs, in 

 consequence of which it is to be supposed that they were already several 

 days old, were received from Havre de Grace at the central station on 

 the evening of June 13. They were immediately placed in an aqua- 

 rium, but many of them died in a day or two after, save about fifty 

 which were transferred by the writer to one of the smaller of the carp 

 ponds in charge of Dr. Kudolph Hessel, where, as Professor Baird had 

 suggested, they might possibly find some food suited to their wants and 

 grow large enough for us to learn something of their future history. The 

 case is an extraordinary one, as the possibility of interbreeding mem- 

 bers of such very distinct families as that of the Clupeoids and Percoids, 

 unless the impregnation took place under the very eyes of the naturalist, 

 might well be doubted, as even such a thing as the successful impregna- 

 tion of the ova would naturally be doubted by those familiar with the 

 recorded facts related of hybrids in general. The evidence in favor of 

 the fact in this case is, however, too strong to be passed over, and until 

 we know more of the later history of this singular hybrid, the follow- 

 ing notes on the differences which were presented by the embryos as 

 compared with those of the true shad must suffice. The striped bass 

 was the male and the shad the female parent. 



Teeth more numerous and more hooked on the lower jaw; at least 

 three pairs, only two pairs in shad of same age. Lower jaw itself longer, 

 with gape of mouth much wider ; ear capsule proportionally much larger 

 than in shad larvae of same age, and otoliths much larger. Tail a little 

 more fan-shaped than in shad of same age, and pigment and fine cellular 

 radii of fins slightly more developed than in the latter. Intestine much 

 more slender, that is, its lumen is much less spacious than in Alosa or 

 Clupea. Liver in about the same position as in larval Alosa, but gall- 

 bladder and eye relatively and perceptibly larger; Meckel's cartilage a 

 fourth longer. General iorm that of the larval Alosa, but head more 

 prolonged and acuminate anteriorly. The preponderance of characters 

 appears to be towards the female parent, and appears to be an undoubted 

 hybrid. The eggs were taken by some of the crew of the steamer Fish- 

 hawk, at Havre de Grace, and were impregnated with the milt of the 

 ''rock" or striped bass, because no ripe shad milters happened to be at 

 hand. 



