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 Young, 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 Ashworth, 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 similar* negative result, — how Mr Ramsbottom, 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 

 came 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 I 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, I procured two charr from Windermere, — a 

 male and female fish, taken from a shoal in the lake, a breeding bed. On gentle 

 pressure to the abdomen, ova in large quantity were obtained, and abundance of 

 spermatic fluid ; 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 

 come 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 w r ater — 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 fcetal 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- 



