THE ORIGIN OF VARIETIES IN SALMONID. 133 
Captain Kirkwood, of Bartragh, when passing in the train over 
the railway-bridge at the Lough near Foxpid, on December 17th, 
saw a herd consisting of between two hundred and two hundred 
and fifty birds. When first observed, he thought they were the 
white breakers of the lake; but, as the train passed within about 
one hundred and fifty yards of them, to his great astonishment, 
he saw that they were Swans. Another friend of mine, near 
Ballyshannon, in Donegal Bay, counted seventy Swans in a little 
inlet of the bay, the week after Christmas; he said they were very 
noisy when feeding, and observed a large number of grey cygnets 
amongst the herd. 
F THE ORIGIN OF VARIETIES IN SALMONIDA:. 
By Francis Day, F.L.S., F.Z.S. 
Tuere is hardly an investigation of more interest to the 
biologist than the study of how local causes induce temporary, or 
even permanent, changes in both animals and vegetables, for the 
purpose of adaptation to new conditions. Among the forms thus 
subject to constant variation, fishes are no exception, as every 
fisherman and pisciculturist is aware. These modifications may 
be due to the quality or quantity of the water in which the finny 
tribes reside; to the nature of the soil over which the water 
passes or remains ; and many other causes that it will be unneces- 
sary to enumerate in detail. I, propose offering a few short 
observations upon the result of keeping some Salmonide, from 
the time of their birth, in a state of unnatural confinement, which 
has induced changes that might cause a museum-naturalist to 
believe that the examples before him were either novelties or 
hybrids between different species. For some there are who 
consider specific rank ought to be accorded to specimens which 
do not coincide with the normal types. Thus, a young Salmon 
with a disproportionately short head and slender body has been 
termed Salmo gracilis. A. Trout, owing to its proportions and 
the extreme muscularity of its stomach, somewhat resembling 
(it has been considered) the gizzard of a gallinaceous bird, first 
received the term of “gillaroo,” as denoting merely a variety, and 
a few years since of Salmo stomachicus, under the impression that 
it is a distinct species, 
