38 History of British Entomostraca. 



we are not aware of the catalogue having been much increased since 

 the publication of this latter work. It surely is not from want of 

 interest belonging to them, that the naturalists of this country have 

 so neglected these curious little animals, for many of them are wor- 

 thy of all admiration. " The multifarious and complicated structure 

 of their body/' says Muller in his admirable work,* " the wonder- 

 ful agility of their members ; the very great fineness of their organs ; 

 their singular method of living and copulating ; their living in wa- 

 ters which our cattle and we ourselves are daily drinking ; the evils 

 which they may give rise to, and which are seen to be inflicted on 

 fishes ; the emoluments, which, although we are in the greatest part 

 ignorant of them, they nevertheless produce in the economy of na- 

 ture ;t that these things are very worthy of being known, scarce anyone 

 will doubt. Not to mention their external similitude to shells, and the 

 natural transition which takes place in them, from insects to testa- 

 ceous 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 

 Pulex aquaticus ? 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 systematic arrangement of the Entomostraca has been a mat- 

 ter of considerable discussion amongst naturalists ; and has varied 

 much according to the various views which authors have adopted. 

 Desmarest, in his work on the Crustacea, published in 1825, has 

 given a tabular view of the various arrangements which different 

 authors have suggested, from Linnaeus to his own time. In the last 

 method adopted by Latreille in the fourth volume of Cuvier's 

 Regne Animal, published in 1829, the following is the arrangement, 

 and in it are, I believe, embodied almost all the genera introduced 

 by his predecessors. Of the great class '■'■ Crustacea," he forms two 

 general divisions, the " Malacostraca," and " Entomostraca." The 

 Malacostraca he divides into five orders, " Decapoda, Stomapoda, 

 Amphipoda, Laemodipoda, and Isopoda;" the Entomostraca, into 

 two, the " Branchiopoda and Psecilopoda." The order Branchio- 

 poda contains those genera which have organs proper for mastica- 

 tion, are possessed of branchiae attached to the feet or jaws, and are, 



* P. 4. 



f " It is the common opinion, that it is the Caligi which force the salmon 

 from the sea up rivers towards the waterfalls. " 



