60 Linruean Society. 



the Salmon. From about midsummer, but more especially with the 

 autumnal floods, Salmon and Sea Trout of various sizes begin to 

 rush up the freshwater streams and rivers, their object being clearly 

 to make their way to the place of their birth, there to provide for 

 the propagation of their species. From the time the Salmon enters 

 the fresh water it ceases to feed, properly speaking, although it may 

 occasionally rise to a fly, or be tempted to attack a worm or min- 

 now, in accordance seemingly with its original habits as a smolt. 

 But after first descending to the ocean and tasting its marine food, 

 it never again resorts to its infantile food as a constant mode of 

 nourishment. This great fact, well understood by fishermen and 

 anglers, has been placed by Mr. Young of Invershaw beyond all 

 doubt. Nothing is ever found in the stomach or intestines of the 

 fresh sea Salmon but a little reddish substance, and this Dr. Knox, 

 after a careful microscopic examination, concluded to bfe the ova 

 of some species of Echinodermata. Of the Salmon, while in the sea, 

 this is therefore the sole and constant food. Sea Trout also live on 

 it, but they readily take to other food even in the sea, such as 

 sand-eels, herring-fry, &c. The absence of this kind of food forms 

 an insurmountable obstacle to the preservation of Salmon and of 

 some kinds of Sea Trout in freshwater lakes. M. Valenciennes de- 

 scribes the Salmon as voracious, and states that its food consists of 

 fishes — Ammodytes Tobianus ; but Dr. Knox maintains that there 

 exists not a single fact in the history of British Salmon to support 

 this opinion. He refers to various fanciful theories suggested by 

 fishermen and others in regard to the marine food of the Salmon ; 

 and concludes by stating that in spring, as the spawn fish are 

 descending with the smolts, they may occasionally be tempted with 

 an artificial fly or lob-worm, but as to their feeding regularly in 

 rivers, Mr. Young's experiments have negatived the assumption be- 

 yond all doubt. 



With regard to the Entomostraca themselves, they are abundant 

 in the sea as well as in freshwater lakes ; and it is easy to see by 

 their remains in the limestone of Burdiehouse and of other quarters 

 that they played an important, perhaps the same, part in the ceco- 

 nomy of the ancient world as they do in this, serving as food namely 

 to countless shoals of gregarious fishes, which abounded then as 

 now in fresh and in marine waters. The Entomostraca of the 

 Southern Hemisphere differ seemingly from those of the Northern; 

 that they serve there also as the food of gregarious fishes was proved 

 by the author's brother many years ago in respect of the so-called 

 Herring of the Bay of Islands. They vary considerably in size, and 

 seem to extend from pole to pole, consuming the organic remains, 

 which but for them might speedily infect the ocean itself. 



The paper was accompanied by magnified drawings of the species 

 of Entomostraca found in the stomachs of the Vendace and of the 

 Herring. 



