214 



EVENDfGS AT THE MICROSCOPE. 



confined to the base. These minute creatines, iu this 

 earl}' state of their existence, are natatory and wonder- 

 fullj active. They are continually swimming from one 

 part of the vessel to the other, and when observed free 

 in their native pools, are, if possible, even more active 



6EC0XD STAGE OF SHOEE-CEAB. 



than when in confinement. Their swimming is pro- 

 duced by continued flexions and extensions 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 examina- 

 tion. As the shell becomes more solid thev £:et less ac- 

 tive, and retire to the sand at the bottom of the vessel, 

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



