2 DR DAVY ON THE IMPREGNATION OF 
mon which had not been mixed with milt after exclusion, though in all other 
respects placed and treated like other ova from the same fish,—ova which had 
been mixed with milt after their exclusion, and were thereby impregnated, and 
rendered prolific. 
Mr Youna, in his Natural History of the Salmon, gives an account of some 
experiments with a similar negative result. In page 17, he states, “We have 
often experimented on the ova of fishes, merely to arrive at facts. We have im- 
pregnated one part of the ova of the fish with milt, and have left part unimpreg- 
nated, and then deposited both parts in the same stream, at the same depth, and 
in a current of exactly the same velocity. But never, in any one instance, did we 
find one grain of the unimpregnated part productive, while the other portion that 
was impregnated with the milt never failed to produce fry in due time.” He 
adds, “ This has been frequently tried. and has at all times proved the same.” 
Mr Asuworru, by whom the production of salmon on a large scale has been 
so successfully carried on in Ireland, informs me, in a letter with which he has 
favoured me, of a similarsnegative result,—how Mr Ramssorrom, in his employ, 
“took a female fish (a salmon) and extracted a quantity of eggs; then placed 
them in a box alone, without impregnating them with the milt, and none of them 
eame to life; and how “he took the remainder of the ova from the same fish, 
and impregnated them with the milt, and these produced young fish.” 
The trials | have made have afforded similar negative results. I shall men- 
tion three in particular. 
On the 10th of last November, from a stream in’ which there were known to 
be male fish with mature milt, two female trouts were taken with fully formed 
ova,—ova that were expelled by the application of gentle pressure to the abdo- 
men. These were placed on gravel in a glass vessel with water, which was changed 
twice daily; they exhibited no marks of development, and one after another 
became opaque from imbibing water. 
On the 25th of the same month, [ procured two charr from Windermere,—a 
male and female fish, taken from a shoal in the lake, a breeding bed. Gn gentle 
pressure to the abdomen, ova in large quantity were obtained, and abundance of 
spermatic fiuid ; each fish at the time was alive. A portion of the ova was placed 
in three glass vessels with gravel and water, without having been allowed to 
eome in contact with the milt. Another portion of them was mixed with the 
milt, and similarly distributed. The vessels were kept in a room of pretty equable 
temperature, which ranged from about 51° Fahr. to 44°, that is, from the com- 
mencement to the present time, and the water—spring water—was changed 
daily once, and no oftener. Now, January 4th, a large number of the eggs which 
had been mixed with the milt are well advanced, the foetal fish being visible 
in the ova with the naked eye, and this in each of the three vessels; but, on the 
contrary, in the other three vessels, not one egg bears any marks of vital pro- 
