162 LIFE AND HER CHILDREN. 
be terribly puzzled with the number of pieces in 
them, for you will find no less than six pairs. The 
outer pair are evidently altered feet, which are folded 
right over the others so as to cover them in safely, 
much as you might put your hands before your 
mouth ; under these lie two more pairs, with little feelers 
attached to them ; under these again are two other 
pairs, rather differently shaped ; and lastly under these 
a stout pair of jaws, with sharp edges for biting, and 
a surface for grinding the food. These jaws do not 
work up and down as ours do, but from side to side 
like the jaws of a bee or ant, and they are most use- 
ful to the prawn in tearing its food. 
But how can he have come by so many ? Let us 
look back for a minute to the worm, which you will 
remember had no true head, but only a long upper 
lip, and a line of rings on its body, each bearing its 
own pair of bristles. Now, the prawn also is a ringed 
animal, only that in his head the separation between 
the rings is lost, and in his thorax they have grown 
closely together so that we can only count them by 
the lines under his body, and by the limbs, which grow 
one pair to each ring. Thus, wherever there has been 
a ring, there a pair of jointed limbs remains, altered to 
suit the wants of the animal, and as the head is made 
up of many rings, these come close together, and 
form the eye-stalks, the antennae, antennules, and the 
mouth-pieces ; while the five rings of the thorax bear 
the five pair of jointed legs, and the swimmerets and 
tail-pieces spring from the rings of the abdomen. 
While all the Crustacea keep to this rule of a 
pair of jointed limbs to each ring, the changes are 
endless by which these rings and these limbs have 
