n8 THE CRUSTACEA 



moults, in the course of which the little animal undergoes con- 

 siderable change and development, it becomes a zocea, and is 

 furnished with maxillae and two pairs of jaw-feet. After a further 

 series of moults the Prawn enters the third stage and passes from 

 the zocea to the mysis form, in which the paired eyes, all the append- 

 ages of the mouth and head, the segments of the thorax, and the 

 rudiments of the feet appear, and at last the adult stage is reached. 

 Nothing could be more dissimilar in appearance than the nauplius, 

 zoaea, and adult stages in the life of this Prawn. 



The process of moulting or skin-casting is not restricted to 

 the early stages alone, but is continued in the adult, the shelly 

 coat being cast off and renewed as often as the growth of the 

 animal renders its enlargement necessary. Crabs and Lobsters, 

 when about to cast their armour, seek out some quiet hiding- 

 place, and cease for a time to feed. Then the old coat of mail is 

 thrown off, the animal emerging from it weak and exhausted by 

 its struggles, but with the new coat ready formed though quite 

 soft. As the animal rests beside its cast-off coat, it looks so much 

 larger that one wonders how it could have been contained therein, 

 and certainly it must have felt very uncomfortable. The new 

 coat is at first soft and membranous, but soon becomes encrusted 

 with calcareous matter, and as hard as the old one. The Crustacea 

 also possess the power of reproducing injured or lost limbs. The 

 perfect restoration is not immediately effected, but is gradually 

 accomplished in the course of several moults. 



The Crabs are in many respects the most interesting and in- 

 telligent members of the Crustacea, and they vary in size from 

 the tiny Pea Crabs, little more than a quarter of an inch in diameter, 

 to the giant Spider Crab of Japan (Macrocheira Kempferi), which 

 measures 10 feet between the tips of the clawed fore-limbs. The 

 Spider Crabs are a most interesting group, though not so active 

 in their movements as their long and slender legs might lead one 

 to suppose. Many of these Crabs are quite covered with a living 

 growth of seaweeds, sponges, and hydroids, and, thus disguised, 

 are enabled to stalk their more active prey unobserved, drawing 

 stealthily nearer, until with a sudden dart the victim is pounced 

 upon and firmly grasped by the small, slender claws. The Spider 

 Crabs vary a good deal in length of limb, as can be seen by the 

 photographs of Macropodia rostratus, the Long-legged Spider Crab, 





