160 
CRUSTACEA. 
bits transverse cells formed by crustaceous laminae, and separated in 
their middle by a longitudinal range of the same nature. 
Tlie sexual organs of the male ai’e situated near the origin of the 
two posterior feet. Two articidated pieces, of a solid consistence, 
and resembling horns, stylets, or setaceous antennae, placed at the 
junction of the tail with the thorax and replacing the first pair of 
subcaudal appendages, are regarded as the male organs of copulation, 
or at least as their sheaths. But, according to our observations on 
various Decapoda, each of them consists of a little membranous body, 
sometimes setaceous, and at others filiform or cylindrical, that pro- 
jects from a hole situated at the articidation of the hip of the two 
posterior feet, with the lower shell. The two vulvae are placed on 
this piece, between those of the third pair, or on their first joint, a 
disposition depending on the widening and narrowing of the lower 
shell. Copulation takes iAd.ce, ventre a ventre. These animals grow 
but slowly, and live a long time. It is among them that we find the 
largest and most useful species, but their flesh is not easily digested. 
The body of some Palinuri attains the length of a metre. Their 
claws are efficacious weapons, and have such power in large indivi- 
duals, that they have been seen to seize a goat, and drag it from the 
shore. They usually inhabit water, but do not instantly perish when 
deprived of it; some species even pass a part of their lives on land, 
only visiting the water in the nuptial season, and for the purpose of 
depositing their spawn. Even they are compelled to fix their domicile 
either in burrows, or in cool, damp places. The Decapoda are vora- 
cious and carnivox’ous. Certain species even penetrate into ceme- 
tries, and devour the dead. Their limbs are regenerated with sur- 
prising promptitude, but it is requisite that the fracture be at the 
junction of the articulations, and when accident determines it other- 
wise, they know how to apply a remedy. When they wish to change 
their skin, they seek a retired and solitary spot, in order to be shel- 
tered from their enemies, and to remain at rest. "When the change 
is effected, their body is soft, and has a more exquisite flavour. A 
chemical analysis of the old shell proves it to be formed of the car- 
bonate and phosphate of lime, united in different portions with gela- 
tine. On these proportions depends the solidity of the shell ; it is 
much less thick and flexible in the latter genera of this order, and 
further on, it becomes almost membranous. M. de Blainville has 
observed that the shell of the Palinurus is composed of four superin- 
cumbent layers, the superior and two inferior of which are mem- 
branous ; the calcareous matter is interposed between them, forming 
the fourth. Exposed to heat, the epidermis becomes of a more or 
