Chapter VII.— THE GREAT FORCEPS OR BIG CLAWS. 
THE CRUSTACEAN CLAW. 
The last ten thoracic legs of higher Crustacea all end in hard-pointed segments 
technically known as dactyls. In the account which follows, when not thus desig- 
nated, they will be called “single claws,” “nails,” or “digits,” the original meaning of 
the word. In Palinurus, the spiny lobster, all of the thoracic legs end in talon-like 
claws of this simple type; but in the true lobsters, crayfishes, crabs, and many other 
decapods a unique organ is developed in certain of the forward legs by the extension of 
an opposable finger-like process of the subterminal segment, the propodus, which is 
often large and powerful. In the great cheliped of the lobster (pi. xxxiii and xxxvii) 
this division is also called “the hand” and the terminal part of it the “index,” as dis- 
tinguished from the opposed “thumb” or dactyl. Thus is formed the admirable 
forceps, commonly known as the “claw” or chela.® 
Those legs ending in forceps are described as chelate and the others as nonchelate, 
and the technical use of these terms is unobjectional. This, however, need not lead to 
the ambiguity of saying that the last two pairs of legs in a lobster or crayfish have no 
“claws.” To avoid this absurdity, we may adopt Huxley’s terms, “ double claws ” and 
“single claws” for the forceps of the first three and the nails of the last two pairs of 
legs, respectively, since they describe the conditions met with in both lobsters and cray- 
fish exactly. The chelate legs all pass through the simple claw stage in either the egg or 
early larval state. 
The big claws of the lobster are remarkable organs whether considered in the light 
of their structure, their development, or the process of their renewal, and the more we 
study them the more remarkable they appear. 
In most of the higher Crustacea the great claws are the chief weapons for both 
attack and defense and very efficient means for seizing and rending the prey, as well 
as for grasping and holding the female in the act of pairing, when the spermatophores 
are transferred to her seminal receptacle or to some other part of her body. 
While three pairs of pereiopods in this animal bear double claws or forceps, in the 
first pair alone are they entitled to be called “great.” In many crabs, as well as in 
the lobsters and crayfish, the great claws are weapons whose grip is not to be despised. 
In some of the crayfishes the great chelipeds are equal to about one-quarter of the 
weight of the entire animal, while in lobsters above medium size their proportionate 
weight sometimes reaches one-half, and tends to increase with age. Moreover, the 
disproportion between the big claws of either side, which are normally asymmetrical, 
« Latinized from the Greek word for any armed appendage; in plural form chelee, corrupted from chele. 
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