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Show 1884.] HYBRIDS AMONG THE SALMONID.E. 27 1875, and placed in the island-pond in 1879, when it was finally completed. This pond is 210 X 90 feet, and from 10 to 11 feet deep in the centre. One can hardly assert that the fish thus kept have been under the same conditions of existence as if they had been in a wild state in Scottish waters. Always provided with food, they may have thus been somewhat stimulated, and their powers of propagating their species accelerated. This may tend to shorten life, as sterility in fishes appears to lengthen it. It has been apparent that males experience a larger mortality than females, due apparently to exhaustion after breeding, which seems to be assisted by their pugnacious propensities. I last year remarked upon the fact observed at Howietoun, that, as a rule, the Lochleven variety of Trout gave eggs of different sizes in accordance with the age of the parents. Those which were hatched in 1876, or six years old, were producing ova 32 of which filled the length of a glass quill, whereas those wbich were hatched in 1875, or seven years old, gave ova 27 or 28 of which occupied the same space. Since then I have come across several interesting statements, which fully bear out the observations made at Howietoun. In the Report of the United-States Fish Commission on the McCloud River, for 1878, it is observed that " the parent Salmon were unusually small, their average weight being under eight pounds. This small size was stated to he undoubtedly caused in whole or in part by the fishing at the canneries of the Sacramento, where the 8-inch meshes of the innumerable drift-nets stopped all the large Salmon but let all the small ones through. The eggs when taken proved to be at least a third smaller than those of most previous years, and the average number of eggs to the fish was about 3500 against 4200 in the previous year." In this case the diminished size of the parents may have not only conduced to diminished size of the ova, but likewise to a decreased amount, for the number generally is proportionate to the weight of the parent fish. Livingston Stone adduces another reason for this result, namely, that American Trout, Salmo fontinalis, iivingin spring water (which means deficient food) develop smaller ova than such as reside in brook water. That is, poverty in food has the same effect in diminishing the size of the eggs as if the parent had not yet arrived at full sexual maturity. I adduce these instances because assertion has been so confidently made to the contrary, and it is perhaps as well to be able to bring forward facts observed at different places by different observers who are not acquainted with the views of one another. Malmgren having observed that the ova of Trutta relicta are considerably smaller than those of the Salmon, Dr. Giinther remarked in the 'Zoological Record' (1864, pp. 180, 181) as follows:-"Thirdly, as Hr. Malmgren observes, in the size of the ova. The last character will be considered very significant by all who may have a more extensive knowledge of fishes, as the size of the ova is not only invariably the same in |