THE METAMORPHOSES OF CRUSTACEA 69 



out from the middle of the back, and another pro- 

 jecting, like a beak, in front. 



The narrow abdomen or tail is very flexible, and 

 can be doubled up under the body or stretched out 

 behind; it ends in a forked telson. There are two 

 pairs of swimming limbs, each with endopodite and 

 exopodite, and the short antennules and antennae 

 are seen on either side of the rostrum. There are a 

 pair of very large compound eyes, which are not set 

 on movable stalks, but are under the front part of 

 the carapace. The two-branched swimming feet are 

 really the first and second maxillipeds (the mandibles, 

 maxillulae, and maxillae, can be found in front of 

 them), but none of the other thoracic limbs are yet 

 developed, and, although the somites of the abdomen 

 are distinct, there are no swimmerets. This type of 

 larva is known as a zoea, a name which was given 

 to it when it was supposed to be an independent 

 species of Crustacean. As a matter of fact, the zoea 

 just described is not quite the earliest stage of the 

 Shore Crab, for when hatched from the egg it is 

 without the spines on the carapace, and is slightly 

 different in other respects. A few hours after hatch- 

 ing, however, it casts its skin for the first time, and 

 becomes a fully-formed zoea. It swims rapidly about 

 at the surface of the sea, feeding on the minute 

 floating animals and plants which are found there,' 

 and growing in size with repeated castings of its 

 skin. In the later stages of the zoea the rudiments 



