Fishes. 4723 



M. Valenciennes remarks, in his great work on Fishes, that the salmon 

 is "vorace; sa nourriture consiste en poissons; (annodytus tobianis.") 

 There exists not a single fact in the history of British salmon in sup- 

 port of this opinion. 



In the absence of positive evidence in respect of the marine food of 

 the salmon various theories have been invented by ingenious men, 

 fishermen, closet naturalists, amateurs, and others, to explain the well- 

 known fact of the seeming emptiness of the stomach and intestines in 

 the high-conditioned fresh-run salmon. These theories require no 

 refutation. Some imagined that the salmon refrained from eating in 

 order to prepare himself for his ascent up the river; we owe this 

 singular fancy to Sir Humphrey Davy. Others imagined that the 

 digestive powers of the salmon resembled a furnace, consuming in an 

 incredibly short space of time all the little fishes they swallow ; as the 

 intestines are empty as well as the stomach, they were obliged to assign 

 to the salmon's stomach a power equal to the digestion of indigestible 

 parts, such as the skeleton, lens of the eye, &c. Lastly, some con- 

 jectured that the salmon discharges, on being taken, the contents of 

 his stomach ; but daily on the Tay at Invershin, and elsewhere, salmon 

 are taken in large numbers at a single haul of the seine ; I have often 

 seen them so taken. Could such a fact, if true, escape observation ? 

 I leave the hypothesis in the hands of the practical fishermen. 



In spring, as the spawned fish are descending with the smolts towards 

 the ocean, they may occasionally be tempted with an artificial fly or 

 lob-worm; but as to their feeding regularly in rivers, Mr. Young's ex- 

 periments prove, beyond all doubt, that if they feed they profit nothing 

 by it, losing weight and strength daily during their sojourn in the fresh 

 waters. 



Of the Entomostraca themselves.* 



The object of this memoir being simply to establish the fact that 

 many valuable gregarious fishes live, some exclusively, others partly, on 

 the Entomostraca, it is not my intention to say much respecting the 

 minute shell-fish serving as their food. They were first admirably de- 

 scribed by Miiller and Jurine, and their natural history is tolerably well 

 known. They must be exceedingly prolific, and breed no doubt many- 

 times a year : they are abundant in the sea as well as in fresh-water 



* Engravings of the specimens of the Entomostraca first discovered in the ven- 

 dace and herring will be found in my Memoir presented to the Royal Society of 

 Edinburgh. 



