HYBRIDS. 49 



Until recent times the opinion has been very generally accepted that the 

 sterility of hybrids is Nature's mode of preventing the intermingling of species ; 

 for it is apparent that, did not soiTie means exist by which the commingling of 

 forms could be prevented, in a short space of time all distinctions would become 

 obliterated — families, genera, and species would be inextricably mixed up.* But 

 among fishes causes exist, as to seasons, localities, ova, and milt, but which it is 

 unnecessary to again detail, that greatly tend to circumscribe such commingling. 



40 per cent, of J'oung fish, but more if the milt of the char were employed. The ova of a hybrid 

 between a trout and a char could not be fertilized by means of trout milt. Carl Peyrer (1876) 

 stated that in Upper Austria " artificial fish-culture had produced many cross-breeds, especially 

 of the char, Sahno salveliniis, with the trout, which excel the pure breed in many respects. In 

 Upper Austria the eggs of the char are mostly impregnated with the milt of the brook trout." 



Leuchart remarked that in January, 1878, some salmon ova were fertilized with trout milt, and 

 the offspring were kept in a private brook, well protected from the ingress of strange fish. In the 

 beginning of 1879 seventy of them were transferred from the water in which they then were, into 

 a small perfectly inclosed pond, wherein they remained until January, 1880. On taking the 

 fish from the pond, only fifty-four were found, and a portion of the larger ones had effected their 

 sexual development. Only one example was a female, while twenty-five milters were counted 

 (possibly the missing ones were females which had jumped out of the water at night-time and 

 been carried off by vermin). On Feb. 7 the ova of the female was milted from one of the males. 

 In the middle of March the eyes of the embryo were visible, and shortly afterwards the hatched 

 fry, along with their parents, were brought to Berlin in spirit. In this instance the male parent 

 was a trout, and trout of both sexes commence breeding at two years of age, as was hero observed 

 to be the case, the importance of which has been referred to. In the Berlin Fishery Exhibition 

 (1880), were some lovely fish, crosses between the char and the trout, and shown by Professor 

 Haack, who is s:'id by Leuchart to have observed a capacity for impregnation of the ova of hybrid 

 salmon with one of the parent species. 



The Hon. Robert B. Roosevelt observed (Proceedings of the ^American Association for the 

 Advancement of Science, vol. sxxiii, 1884) that " the crosses made under the New York State 

 Fishery Commission have been very numerous. The first was that of the California salmon 

 (Saimo qninnat) and the brook trout (Salmo fontinalis): this was in the year 1870. Then came the 

 cross of the salmon or lake trout {Salnm confinis) with the brook trout : then the California trout, 

 Sahno irideus and the brook trout : and thereafter the entu-e range of the salmon and trout 

 families, as far as they were within the reach of the operators, were combined in many and 

 curious proportions." 



The earliest hybrids to mature their ova were the cross between the male California salmon 

 and the female brook trout. This took place in the year 1879. They not only became gravid 

 but ascended the spawning races as naturally as those of either distinct species. But as they 

 deposited no eggs and did not appear to mate, an examination was made, and it was ascertained 

 that they were all females. To remedy this a number of male spawning brook trout were 

 admitted to the same race-way. The nests had been constructed but no eggs had been deposited 

 in them. A further examination proved that the eggs were too large to pass the ovarian opening. 

 When they were extruded by force, as in the stripping process, the shells were crushed and a few 

 which were obtained by the use of the knife, a sort of modified Caisarean operation, and were 

 brought into contact with the milt of the trout, failed to impregnate and perished. In all 

 subsequent operations, however, the proi»rtion of each sex has been about equal. 



The cross of the male brook trout and the female salmon trout, the Salmo fontinalis with the 

 Salmo conjinis, matured ova in October, 1880. There were about 72,000 eggs cast which hatched as 

 readily as those of either parent, although it was found that a larger percentage of them could be 

 impregnated with the milt of the male brook trout than with the milt of their own kind. The 

 percentage of fertility was good, and the young proved to be perfectly healthy and as able to 

 stand the struggle for existence as any of their brethren of pure strain. At the first cross one- 

 half of the salmon trout was eliminated, their young impregnated with the milt of the male 

 brook trout left only a quarter of the coarser parent, and then came those which were seven- 

 eighths brook trout to one-eighth salmon trout, which is as far as we have got at the present time. 

 The young of each of these generations show the effects of the cross. The first in descent had 

 none of the carmine specks which are the distinguishing feature of the " speckled trout" of our 

 brooks. In the second generation the spots began to appear, and in the last they are distinctly 

 visible, although fewer in number than in the trout of Sancjre Azul. In the year 1883 there were 

 distributed to the brooks of the State 45,300 hybrid fry which were one-half salmon trout and 

 one-half brook trout, and in 1884 a second planting of 79,000 three-quarter brook trout was made. 

 The first, which were deposited in wild waters, were found in six months to have attained a 

 growth of four and a half inches in length, equal to the growth of a brook trout in the same 

 water for an entire year. 



* Mudie observed [Popular Guide to the Ohseri'ation of Nature, 1832) that " the mules of whatever 

 they are hybrids, will not breed as a race, though they generally can with either of the parent 

 stocks, and the result is a partial return to that stock : and if the system were continued, the 

 ultimate progeny would be again assimilated or identified with the pure blood." Dr. Giinther 



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