BULLETIN OF THE UNITED STATES FISH COMMISSION. 237 



younnf fishes and very many adult forms, I find tbat the almost unani- 

 mous testimony of various observers is to the effect that these creatures 

 are larg^ely carnivorous, and subsist mostly upon protozoa, or the low- 

 est grade of animal existence. In proof of the foregoing, the following 

 extracts are here introduced. 



lu his Natural History of the Biitish Entomostraca, page of the 

 introduction, Dr. W.Baird remarks: " I have no doubt that most of the 

 entomostraca are essentially carnivorous, and I have frequently seen 

 specimens of CyrrHs in their turn, as soon as dead, attacked immediately 

 bj' quantities of Cyclops quadricornis, which in a few minutes had fast- 

 ened themselves uijon the dead animal, and were so intent upon their 

 prey that they were scarcely frightened away from it by being touched 

 with a brush. In a short time the Cypris might be seen lying at the 

 bottom of the vessel, the valves of the shell separated and emptied of 

 its contents. Leeuweidioek and I>e Geer not only maintain that the 

 Cydops quadricornis lives upon animalcules, but that it even preys upon 

 its own young, a fact which I have also noticed myself. Jurine asserts 

 that the Cyclops quadricornis is carnivorous from taste, and only her- 

 bivorous from necessity; while the Daphnia ptdex^ he distinctly affirms, 

 lives upon animalcules. Place a few Entomostraca, such, for example, 

 as the Dapliiiia', Chirocephali, Lyncei, «&c., in a vessel with pure, clear 

 water, and only some A'egetable matters in it, and they gradually be- 

 come languid, transparent, and finally die; but mix with this water 

 some which contains numerous Infusoria, and the Entomostraca will 

 then be seen speedily to assume another aspect. They become lively 

 and active, and the opacity of their alimentary canal testifies sufficiently 

 the cause of it. When, indeed, we consider the amazing quantity of 

 animals which swarm in our ponds and ditches, and the deterioration of 

 the surrounding atmosphere which might ensue from the putrefaction 

 of their dead bodies, we see a decided fitness in these Entomostraca 

 being carnivorous, thus heli)ing to prevent the noxious effects of putrid 

 air which might otherwise ensue ; whilst they in their turn become a 

 prey to other animals which, no doubt, serve their purposes also in the 

 economy of nature." 



"The food of the Lynceidw,''^ says Baird, "consists of both animal 

 and vegetable matter, and while they prey upon animalcules smaller 

 than themselves, they, in their turn, are devoured in great numbers by 

 insects larger than they are." 



According to Pritchard, the Chyodorus sphaericus is the choice food of 

 a species of fresh-water Nais which he calls Lurco. "So great is the 

 voracity," he says, "of this creature tliat I have seen a middle-sized one 

 devour seven Lyncei in half an hour." 



Referring to the DapJiniada', our author again observes: "The food 

 of these animals, according to Straus, consists of vegetable matter, and 

 not animal ; but I have found that of two groups placed in se])arate 

 vessels of clear water, the one ha^ing only particles of vegetable matter 



