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 Paecilopoda." 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." 
