CRAB. 
491 
taking themselves to a state of retirement, await 
the formation of their new limb. Most of the 
genus are very prolific; the female of the common 
Lobster is said to ])roduce upwards of twelve thou- 
sand eggs each time of laying. In this genus also 
we find examples of deviation from that general 
svmmetry of parts, so conspicuous in most other 
animals, in which the shape of the body and limbs 
on one side exactly corresponds to that of the 
other; many of the Cancri being furnished with 
a pair of clielm or claspers which on one side are 
of an immoderate size, while those on the oppo- 
site side are thin and small ; and in some particular 
species, as the Cancer vocans, &c. the size of the 
large arm is so great as to oblige the animal to 
support it on its back, in which position it is 
generally placed while the creature is walking. 
It may likewise be added that this is a particu- 
larity which is sometimes reversed ; a circum- 
stance which occasionally takes place, as is well 
known, in the univalve shells. 
The principal division of the genus is into 
Brachyin'i and ]\Iacrouri, or the short-tailed and 
long-tailed. Of the former division the Cancer 
Fagurus or large edible Crab affords a familiar 
example. This animal has a smooth body, with 
a notched or crenated thorax, five-toothed front, 
and smooth claws with black tips: it grows to a 
very large size, and inhabits the rocky coasts of 
our own island as well as of many other parts of 
Europe. 
Cancer Grap-ms or streaked Crab is a native of 
