ON CRUSTACEA. 
241 
fishes on which they live. The arguli have three sorts of 
feet ; the first two like cupping-glasses, round, and broad ; 
the second with two hooks, proper for prehension, and the 
others, eight in number, soft, fleshy, and terminated by a fin 
formed of two leaflets. 
Finally, the names of brancliiopods, phyllopa, &c. have been 
appropriated to those entomostraca, whose feet are at once both 
organs of locomotion and of respiration. Apus, limnadia, and 
brancliipus, which present this mode of conformation, have 
often a great number of these pill-feet ; there are sixty pair at 
least in apus, eleven in brancliipus, and two-and-twenty in 
limnadia. They are all composed of several thin and soft 
lamina?, diversely configurated, articulated together, and one, 
at least, of their edges furnished with numerous hairs. In 
apus, the first ot these feet have four articulated threads, the 
two upper resembling antenna? ; all the others have, under- 
neath, near their base, an ovaliform, vesicular sac, and those 
of the eleventh pair, support a capsule, with two valves, 
which incloses the eggs. 
These animals, like the insects, have their functions very 
distinct, and accordingly, like them, they should occupy an 
elevated rank in the series of beings. Being provided with 
articulated members, they are evidently in the relation of the 
locomotive faculty superior to the mollusca, and annelides, as 
well as to the radiated and infusory animals. All of them 
possess a nervous system, whose first centres, and first rami- 
fications are easily to be observed. They are scarcely ever 
destitute of the organ of vision. In some of them the organ of 
hearing has been discovered, and every thing goes to prove, 
that the senses of taste and smell exist in the Crustacea, 
as well as in the insects, although the peculiar seats of these 
senses have not yet been recognized. In these respects it is 
certain that the Crustacea have the priority over very many of 
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