CRABS AND SHRIMPS 215 



limited in its extent, and is finally confined to the base. 

 These minute creatures, in this early state of their exist- 

 ence, are natatory and wonderfully active. They are con- 

 tinually swimming from one part of the vessel to the other, 

 and when observed free in their native pools are, if pos- 

 sible, even more active than when in confinement. Their 

 swimming is produced by continued flexions and exten- 

 sions of the tail, and by repeated beating motions of their 

 claws; this, together with their grotesque-looking forms, 

 gives them a most extraordinary appearance when under 

 examination. As the shell becomes more solid they get 

 less active, and retire to the sand at the bottom of the ves- 

 sel, to cast their shells, and acquire a new form. They are 

 exceedingly delicate, and require great care and attention 

 to convey them through the first stage; for unless the 

 water be supplied very frequently and in great abundance 

 they soon die. 



"The second form of transmutation is equally as re- 

 markable as the first, and quite as distinct from the adult 

 animal. In the species now under consideration this sec- 

 ond transformation is marked by the disappearance of the 

 dorsal spine; the shield becomes flatter and more de- 

 pressed, the anterior portion more horizontal and pointed, 

 the three festoons having disappeared. The eyes, from 

 being sessile, are now elevated on foot- stalks, the infra - 

 orbital appendages become apparently converted into an- 

 tennae. The claws undergo an entire revolution; the first 

 pair become stouter than the others, and are armed with 

 a pair of nippers," the others being simple; "but the pos- 

 terior pair are branched near the base, and one of the 

 branches ends in a bushy tuft. The tail is greatly dimin- 

 ished in its relative size and proportions, and is sometimes 



