172 Mr Shaw's Experiments on the Fry of the Salmon, 



specimen of six months'' old, taken from the pond on the 7th 

 of November. Its shape indicates a considerable accession of 

 strength, and its approximation to the features of the parent 

 fish becomes more striking. The gill-cover, on examination, 

 will be found exactly similar in shape to the full-grown salmon. 

 On comparing it with the parr in the river, of a corresponding 

 age, no marked difference can be observed. The whole of this 

 family, as well as another family in pond No. 3, are in a state 

 of perfect health, and feed freely on small worms, gentles, &c., 

 with which I have continued to supply them dui'ing the sum- 

 mer.* As nearly as I can judge, the number of the two families 

 amounts to about 100. Pond No. 2. is occupied with another 

 family of the salmon, also produced by artificial impregnation. 

 The history of this family will form the subject of another 

 paper, after I have had an opportunity of verifying the experi- 

 ment by repetition. 



On comparing the parr taken from the river at a correspond- 

 ing period with those taken from the pond, I found that they 

 were uniformly of a darker colour, arising no doubt from the 

 fish in the ponds having been reared in pure spring-water, while 

 the parr in the river have existed ever since their birth in wa- 

 ter of a more impure quality. The surface of their bodies has, 

 therefore, naturally acquired a duskier tinge, a result ])erfectly 

 well known to all practical anglers who have angled in the va- 

 rious rivers in this country. The water of the pond, in conse- 

 quence of being supplied from a spring at no considerable dis- 

 tance, is of a more equable temperature throughout the year 

 than that of the river. The temperature of the former du- 

 ring the winter is seldom below 40°, or in the summer above 

 60°, while the temperature of the river, which is much more 

 under the influence of the atmosphere, is more variable, and 

 reaches to greater extremes both of heat and cold. I appre- 

 hend, however, that the mean temperature may not materially 

 differ; and, while I freely admit that the difference may have 



* The circumstances attending the development and growth of the family 

 in Tond No. 3 so exactly correspond with those of the preceding family, that 

 their history would only be a repetition of the former. I may, however, state, 

 that the individuals in Pond No. 3 are considerably larger than those in Pond 

 No. 1, the difference at the age of six months amounting to an inch. 



