4 BRITISH ENTOMOSTRACA. 



part ignorant of them, which they nevertheless produce 

 in the economy of nature ;* that these things are very 

 worthy of being known scarce any one will doubt. Not 

 to mention their external similitude to shells, and the 

 natural transition which takes place in them, from insects 

 to testaceous animals, who ever knew, before the Cypris 

 was detected, of an insect quadruped? Before the 

 Limulus and Caligus were properly observed, who ever 

 knew of an insect acephalous, or with a head at least 

 scarcely visible ? Who ever imagined of a copulation of 

 two males with one female at one time, such as takes 

 place in the famous Pidex aquaficiis ? or of an animal 

 whose head was all eye, as we see in the Polyphemus ? 

 These and more wonders are to be met with in the history 

 of the Entomostraca." 



The greater number of these little creatures are 

 furnished with Ijranchia?, either to their feet or maxillae, 

 and when noticed in their native habitats may be seen 

 to have them constantly in motion, their action being 

 seldom interrupted. One chief use, therefore, of them 

 in the economy of nature, may be, as Midler says, to 

 ventilate the water day and night ; and as they chiefly 

 reside in standing pools, they may thus be of great use 

 in preventing them from becoming soon putrid. As 

 this may be considered one of the benefits conferred 

 by these insects, it may be useful to know the evils 

 to man they may be likely to produce- Though they 

 are most abundant in stagnant water, they yet occur 

 in considerable numbers in the purer sorts of water that 

 serve as our common drink, and may frequently be seen 

 even in the drinking-water of London, Edinburgh, and 

 other large towns ; and Miiller asserts very gravely, that 

 as we thus drink them alive, and with their eggs, he 

 would not be surprised were we to discover them some 

 day in the human intestines. " The time," he says, " is 

 at hand, when the causes of disease shall not only be 



* " It is the common opiuiou that it is the Caligi which force the salmon 

 from the sen, up rivers towards the waterfalls." 



