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Show 1884.] HYBBIDS AMONG THE SALMONIDAE. 583 were opened, and the ovaries were found quite distended with eggs,almost ripe, but still just adherent. On looking at these fish in the water, some were seen to have black spots over the back as well as on the sides, but others had not. For the last three weeks these fish have been fed on young Lochleven Trout. ^ That Salmon may he reared in ponds, and in due time, if males, give milt, has been universally admitted, but many have denied that females can produce ova without first descending to the sea. Grilse are well known to breed earlier in the cold season than do mature Salmon ; this it has been surmised must be owing to their being fish in which the time for propagating their species has been deferred for a season, or from February or March until the commencement of the following winter in October or November. Experiments at Howietoun have shown that from Salmon-eggs hatched in March 1881 most of the male parr had milt in November 1883 ; while two or three smolts which jumped out of the pond, and so met their deaths, had ova which in suitable places2 would have matured that year. In 1884 all the females it appears would be ready to breed, but did they do so in rivers and had to depend on male Salmon for fecundating their ova, universal sterility would ensue, as the latter fish breed later on in the winter season. The parr of Salmon are not then normally ready for impregnating the ova of mature Salmon, or "to mingle with the river-trout" as Dr. Giinther suggests, but are available to fertilize the ova of the grilse. W e may well ask the question whether it is a physiological necessity, as asserted by Rasch, for female smolts to descend to the salt water before grilse can develop eggs? This theory is held by some, and appears to be rather widely accepted. I have not considered it worth while to describe the grilse at Howietoun reared from Salmon-eggs, but have kept specimens for reference; consequently I am in a position to maintain that from the eggs of the Salmon, parr, smolts, and grilse with eggs have been reared in the Howietoun pond. Of course the views I have held and still hold, that. Salmon are marine forms which, in accordance with their anadromous instincts, come into our fresh waters to breed, as does the Shad, may or may not be correct. The reasons which have induced me to adopt these views I do not propose discussing in this paper; but I would point out that as the descent to the sea is not indispensable to the development of eggs, it therefore cannot be a physiological necessity, and perhaps we may class it among many other instances as "inherited instinct." I have formerly shown that the milt of a young parr (hatched 1881 and milted in 1883) has insufficient vitality to properly fertilize 1 I received tbe following telegram yesterday, Dec. 1st, 1884, from Howietoun :-" Two of the grilse spawned to-day, ova perfect; kept one female as evidence.'' Tliis alludes to one being placed in spirit for future examination by anybody who may be dubious. 2 Perhaps if these fish are kept another year in earth-ponds with a gravel water-course leading to them, more success will be obtained. |