History of British Entomostraca. 41 
the Entomostraca themselves were seen to be full, sufficiently prov- 
ing that they had not fasted during that time. This assertion, how- 
ever, I am much inclined to doubt, at least with regard to some of 
the species, as I have seen dead specimens of Cypris, for example, 
attacked almost immediately upon their being placed in the water, 
by quantities of the Cyclops quadricornis, who, in a few minutes, had 
fastened themselves apparently upon the dead animal, and were so 
intent upon their prey that they were scarcely frightened away from 
it by being touched with the 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 their contents. Leeuwenhoek and De 
Geer not only maintain that the Cyclops quadricornis lives upon ani- 
malcules, but that they also prey upon their own young ; a fact which 
I have also noticed myself. Jurine also asserts that the Cyclops 
quadricornis is carnivorous from taste, and only herbivorous from ne- 
cessity, while the Daphnia pennata he distinctly says lives upon ani- 
malcules. When, indeed, we consider the amazing quantity of animals 
which swarm in our ponds and ditches, and the deterioration to the 
surrounding atmosphere which might ensue from the putrefaction 
of their dead bodies, we see a decided fitness in these Entomostraca 
being carnivorous, thus helping to prevent the noxious effects of pu- 
trid air which might otherwise ensue ; whilst they in their turn 
become a prey to other insects which no doubt serve their purposes 
also in the economy of nature. The fresh water Gammari seem to 
prey upon them, and the Hydrachnae are their decided enemies, for, 
says Muller, " they seize hold of them, when swimming, by their 
feet, and daintily suck the life's blood out of their captives with their 
sharp beaks."* " The Hydra also, and not a few aquatic larvae, lay 
snares for them, and many Vorticellae frequently grievously infest 
them, for they not only adhere, often in heaps, to the members pro- 
jecting beyond the shell, but also nestling themselves within the 
shell, they overspread the whole body with their own colonies, not 
a little retarding the motion and agility of their host."t The trans- 
formation which the young of the genus Cyclops undergo in their 
progress to maturity, the changing their skin, not only of the body 
of the animal but also the whole shell, with various other very in- 
teresting details, I shall not insist upon here, but reserve them for 
a future number under the history of each genus. 
(To be continued.) 
* Entomostraca, p. 8. f Ibid. 
