68 SALMONIA. [SECOND DAY. 



easily known from their darker backs and brighter 

 sides. By degrees,, however, from the influence of 

 food and other causes, they became changed; the 

 young trout of the introduced variety had flesh less 

 red than their parents; and in about twenty years 

 the variety was entirely lost, and all the fish were 

 in their original white state. A very speculative 

 reasoner might certainly defend the hypothesis, of the 

 change of species in a long course of ages, from the 

 establishment of particular characters as hereditary. 

 It might be said, that trout, after having thickened 

 their stomachs by feeding on larvae with hard 

 cases, gained the power of eating shell-fish, and were 

 gradually changed to gillaroos and to charr, their 

 red spots and the yellow colour of their belly and fins 

 increasing. In the same manner it might be said, 

 that the large trout wliich feed almost entirely on 

 small fishes, gained more spines in the pectoral fins 

 and became a new species ; but I shall not go so far, 

 and I know no facts of this kind. The gillaroo and 

 the charr appear always with the same characters; 

 and I have never seen any fish that seemed in a 

 state of transition from a trout to a gillaroo or a 

 charr; which, I think, must have been the case if 

 such changes took place. I hope, after this explana- 

 tion, Physicus will not find any analogy between my 

 ideas and those of a school, to which I am not 



