Natural History. S8d 



deck tliemselves in a nuptial garb, as birds do. The colour of their 

 flesh varies according to the nature of their aliment. This family 

 of fishes feed, as we have said above, especially upon the larvae of 

 aquatic insects, and of small Crustacea. It is in the waters which 

 contain the most of these last, that the most beautiful salmon trout 

 are found. Direct experiments which were made in lakes, have 

 proved, to my satisfaction, that the intensity of the colour of the 

 flesh arose from the greater or smaller quantity of gammarinsB 

 which they had devoured. 



As to the structure of the head, it offers, in the opercular bones, 

 in the surface of the cranium^ and in its proportions relative to 

 the whole body, very excellent characters ; but those, on the other 

 hand, which are taken from the proportional length and size of the 

 jaw-bone, are of no value at all, since the lower jaw is longer or 

 shorter than the upper, according as the fish opens or shuts its 

 mouth ; and this consideration introduced into the characteristics 

 of the family, has very considerably contributed to multiply the in- 

 stitution of species. The hook which forms the jaw of the Salmo 

 Salar is not even a peculiar characteristic of this species, since the 

 full grown males of all the species of the genus present a crooked 

 prolongation of their lower jaw, to a greater or less extent. 



It results, then, from these observations, that the different species 

 of the salmon family, far from being confined within the narrow 

 limits of some small bodies of fresh-water, are, on the contrary, 

 very widely distributed. They also thrive in all climates, at least 

 in all elevations above the surface of the ocean, whether in fresh 

 water or in salt. It is also true, they prefer those situations where 

 the water is limpid. 



Pi^ssessed of these facts, which I had collected with the most 

 minute and jealous precautions, I have tried to determine the va- 

 rious species which are found in the fresh waters of the Continent ; 

 grounding my examination upon the study of the interior organi- 

 zation, and upon the particulars already determined which the in- 

 teguments present concerning the structure of the scales. I have 

 also introduced the shape of the body, and the proportional size of 

 its internal parts, as important accessaries to the description of the 

 species. Of course I cannot enter at present into the details of a 

 minute description. This, in fact, is the investigation of which I 

 propose to give an account in my treatise upon the fishes of the 

 fresh waters of central Europe. I must here confine myself to a 

 short statement of the results I have obtained. 



c c 2 



