70 THE LIFE OF CRUSTACEA 



of the hinder thoracic limbs and of the swimmerets 

 appear as little buds. In the next stage (Fig. 25, B) 

 all the appendages are present, the dorsal spine of 

 the carapace has disappeared, the eyes are stalked 

 and movable, and the animal has all the appearance 

 of a little Crab, except that the abdomen is stretched 

 out instead of being tucked up under the body, and 

 the swimmerets are used as paddles in swimming. 

 In this stage the larva, which is known as a megalopa, 



FIG. 26 LAST LARVAL STAGE OF THE COMMON PORCELAIN 

 CRAB (Porcellana longicornis SEE FIG. 41, p. 113). x 9. (After 

 Sars.) 



swims at the surface of the sea, but later it sinks to 

 the bottom, and, moulting again, appears as a little 

 Crab (Fig. 25, C), with tucked-up abdomen and 

 swimmerets no longer adapted for locomotion. 



Most of the true Crabs (Brachyura) have a larval 

 history similar to that just described, and pass 

 through zoea and megalopa stages which differ only 

 in details from those of Carcinus. The Anomura are 

 also hatched as zoese, and one of the most remark- 

 able forms common in tow-nettings in British waters 

 is the zoe'a of the little Porcelain Crabs (Porcellana 

 Fig. 26). In this larva the carapace has two long spines 



