18G EVENINGS AT THE MICROSCOPE. 



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 vessel, to cast their shells and acquire a new form. 

 They are exceedingly delicate, and require great care 

 and attention to carry them through the first stage ; for 

 unless the water be supplied very frequently, and in 

 great abundance, thev 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 

 second transformation is marked by the disappearance of 

 the dorsal spine ; the shield becomes flatter and more 

 depressed, the anterior portion more horizontal and 

 pointed, the three festoons having disappeared. The 

 eyes, from being sessile, are now elevated on footstalks, 

 the infra-orbital appendages become apparently con- 

 verted into antenna?. 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 posterior pair are branched near the 

 base, and one of the branches ends in a bushy tuft. The 

 tail is greatly diminished in its relative size and propor- 

 tions, and is sometimes partially bent under the body, 

 but is more commonly extended. This form is as nata- 

 tory as the first. They are frequently found congregating 

 around floating sea-weed, the buoys and strings of the 

 crab-pot marks, and other floating substances, both near 

 the shore and in deep water. Their general form some- 

 what resembles a Galathea." * 



Thus, under Mr. Couch's eye, the Zoea had changed to 

 * " Rep. Cornw. Polyt. Sec," 1843. 



