THE METAMORPHOSIS OF A CRAB. ' 215 



hatch, place some of the larvse under the microscope, and 

 examining them very carefully with a high power, notice 

 the larval skin, which conforms very closely to the outline 

 of the body of the zoea except upon the antennules, the 

 antennae, and the telson. The embryonic antennule is 

 very much larger and longer than that of the zoea, and it 

 carries a long, hairy branch, and a second much shorter 

 branch. The antenna of the embryonic skin is also very 

 much larger than that of the zoea. It divides near its 

 base into two branches, one of which is short and blunt, 

 while the other ends in three long, plumose, swimming- 

 hairs. The telson of the embryonic skin is also very much 

 larger than that of the zoea, and is a slightly-forked fan- 

 like organ, with seven pairs of large, transparent, swim- 

 ming-hairs, five of them plumose. 



n. The Older Zoea. 



The zoea sheds its skin a number of times, the bud-like 

 rudiments of the third maxillipeds and pereiopods grow a 

 little, and the portion of the body which carries them be- 

 comes obscurely divided into segments, the abdominal feet 

 or pleopods make their appearance as pairs of buds on the 

 ventral surface of the abdominal segments, and the endo- 

 podite or flagellum appears upon the antenna, and the palp 

 on the mandible. 



For a number of moults the change of the larva is 

 gradual ; but after a time it sheds its skin and becomes 

 suddenly converted into a larva which is quite different 

 from the zoea, and which is known as a Meyalops. 



II. The Mecjalops Stage (Fig. 110). The megalops 

 larvae may easily be reared from zoeas, or they may be 

 obtained by surface-collecting. They are able to swim 

 actively, but they frequently cling to the sides of the glass 

 beaker, where they may be recognized by their resem- 



