476 Dr KNOX on the Natural History of 



them,) was truly surprising, and to me inexplicable. I should 

 presume it probable, that as these larva? of insects, for such they 

 mostly are, rise above the gravel to assume new forms, they offer 

 ready food to the trout and salmon fry of all sizes which may be 

 in the river ; but I do not suppose that these -fishes dig under the 

 gravel in search of food at any time. Of the ova, taken up a 

 number were brought to town with the utmost care, some pre- 

 served in moss and others in water. The journey occupied about 

 six hours, and being made in a carriage, and all possible care 

 taken of them, it is difficult to assign a reason for the death of 

 these ova, which took place without exception, for none of them 

 ever became developed. Two circumstances might affect them : 

 first, the agitation and shaking ; and, secondly, the change in the 

 nature of the water. A very fine collection of ova, taken from 

 the Kale, and sent me about the same time by a friend, shared 

 the same fate ; they were brought to town very carefully, but 

 closely packed in a large phial in water, and by coach. In the 

 mean time, the ova left in a house situated on the banks of a 

 river, from the bed of which they were taken, lived and became 

 developed. I may here remark the following very singular cir- 

 cumstances. It is said by Sir H. DAVY, on the authority of a 

 person of the name of JACOBI, whose writings I have not met with, 

 that the ova of salmon are deposited in the gravel of rivers under 

 streams, in order that they may be perfectly aerated or exposed 

 to water which is so. This reason, which appears so plausible, 

 is probably not the true one. Ova taken from the bed of a 

 river at any time, from January to March inclusive, and not 

 shaken or carried far, will li ve and become developed, t. e. grow 

 to fish of about an inch in length, in a small glass full of water, 

 changed not oftener than once a-week. They become developed 

 early or late, i. e. varying a week or ten days, according to the 

 temperature of the room in which they are placed. They will 

 appear ten days or a fortnight sooner if placed in a warm room. 



