398 THE AQUARIAN NATURALIST. 



cession of bounds, after the same manner as the 

 Water-flea, Daphnia, and other freshwater Entomo- 

 straca, but particularly Cyclops, whose swimming-feet 

 are extremely analogous. The tail, which is usually 

 bent up under the belly, is short, composed of two 

 joints, and terminates in four bristle-like appendages ; 

 these are employed to assist in progression. 



The most startling circumstance, however, in the 

 structure of these larvae is the possession of eyes, 

 which, although constantly shielded by the valves of 

 the shell, are pedunculated as in the Crab and Lobster, 

 and placed anteriorly at the sides of the body. 



Under the impression that the little creatures re- 

 presented in the plate referred to were Crustaceans, 

 perhaps in a larval state, a few of them were placed 

 by Mr. J. V. Thompson, who first discovered and de- 

 scribed these strange proceedings, in a glass vessel, 

 covered by such a depth of sea-water that they could 

 be examined at any time with a magnifying-glass ; 

 and on the 8th of May (we give the date, in order to 

 indicate the proper season for such researches), two 

 of them were found to have thrown off their exuviae, 

 and were seen firmly adhering to the bottom of the 

 vessel, changed into young Barnacles. 



On the 10th another individual was seen throwing 

 off its shell, and attaching itself, like the others, to 

 the bottom of the glass. As the shelly valves of the 

 young Barnacle are formed, the eyes disappear, and 

 the capability of vision is extinguished for the re- 

 mainder of the creature's life ; the arms at the same 

 time acquiring the plumose appearance characteristic 

 of the adult Cirriped. 



