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III. Some Observations on the Ova of the Salmon, in relation to the distribution of 
Species ; in a letter addressed to Charles Darwin, Esq., M.A., E.P.R.S. ^c. 
By John Davy, M.D., F.R. S., Inspector- General of Army Hospitals. 
Received March 27, — Read April 26, 1855. 
My dear Sir, 
In a letter with which you have favoured me, that of the 28th of January, you did 
me the honour to ask my aid in an inquiry in which you take an interest, in common, 
as you remark, with most naturalists, viz. the geographical distribution of species, 
especially that of fish. At the same time you expressed your opinion that some 
useful information might be procured by experiments on the impregnated ova of the 
latter, were they so conducted as to show what the ova are capable of bearing with- 
out loss of vitality, and under exposure to circumstances such as might be com- 
patible with their being conveyed from one river or lake to another, adhering, for 
instance, to the plumage, beak or legs of birds. In reply, I acquainted you of my 
willingness, should I have an opportunity, to accede to your wishes ; and, that occur- 
ring, having been so fortunate as to procure the means of making some experiments 
likely to be elucidatory, I have now the pleasure of communicating the results ob- 
tained. 
All the experiments I have to describe have been made on the ova of the Salmon, 
for which I have been indebted to two gentlemen, John Barker, Esq., of Broughton 
Lodge in Cartmel, and William Ayrton, Esq., of Chester. By the first, through one 
of his keepers, I was supplied with a considerable quantity of ova, taken from a 
breeding-bed in the Leven, a river that flows out of Windermere, and from a part of 
it near Newby Bridge, about eighteen miles distant from my house. Through the 
latter I obtained ova from Overton on the Dee, taken from boxes in which they had 
been placed in the process, as it has been called, of artificial breeding. 
Both gentlemen were so good as to desire the keepers, in packing the ova, to 
attend to the directions I gave in writing, with the intent of commencing the inquiry 
even in the act of their being sent. Those from the Leven were divided into three 
portions; one, of 110 ova, was contained in an eight-ounce vial, two-thirds full of 
water, which was changed more than once on the way ; another, of 75 ova, was 
enclosed in wet wool ; and the third, of 62 ova, in dry wool. The latter two were in 
a small box, the lid on, which box as also the bottle were carried by hand. These 
ova reached me in about twenty-four hours from the time they were taken from the 
river, and were received on the 6th of February. They all appeared healthy and in 
