22 THE NATURAL HISTORY OF THE COMMON CRAYFISH 
be chelate. The two hindermost pairs, on the other 
hand, end in simple claws. 
In front of these legs, come the great prehensile 
lunbs (10), which are chelate, like those which im- 
mediately follow them, but vastly larger. ‘They often 
receive the special name of chele; and the large terminal 
joints are called the “hand.” We shall escape confusion 
if we call these limbs the forceps, and restrict the name 
of chela to the two terminal joints. 
All the limbs hitherto mentioned subserve locomotion 
and prehension in various degrees. ‘The crayfish swims 
by the help of its abdomen, and the hinder pairs of ab- 
dominal limbs ; walks by means of the four hinder pairs 
of thoracic limbs ; lays hold of anything to fix itself, or 
to assist in climbing, by the two chelate anterior pairs of 
these limbs, which are also employed in tearing the food 
seized by the forceps and conveying it to the mouth; 
while it seizes its prey and defends itself with the forceps. 
‘The part which each of these limbs plays is termed its 
function, and it is said to be the organ of that function ; 
so that all these limbs may be said to be organs of the 
functions of locomotion, of offence and defence. 
In front of the forceps, there is a pair of limbs which 
have a different character, and take a different direction 
from any of the foregoing (9). These limbs, in fact, are 
turned directly forwards, parallel with one another, and 
with the middle line of the body. They are divided into 
«x number of joints, of which one of those ncar the base 
