CIRPxIPEDES. 79 



other proofs that they arc so ; these arc derived from the 

 structure of the mouth (pi. X. fig. 4. 5. 6.) and from the 

 fact of their throwing off their exuvia exactly after the 

 manner oftlie otlicr members of this class, a circumstance 

 hitherto denied, but of which any person may be easily 

 satisfied. During the whole of the spring and summer 

 months, the water teems with these exuvia of Tritones, 

 (the animal-inhabitant, according to Linnaus, of the Bar- 

 nacles)— it is impossible to avoid drawing up numbers every 

 time a towing net is thrown out, nay the tide is at times 

 discoloured from their abundance ; but to be certain that 

 these are really such, let a stone with several barnacles 

 upon it, be kept in sea water, regularly renewed, towards 

 the latter end of April or the beginning of May, and with due 

 attention many of them may be observed in the act of 

 throwing off exuvia in every respect identical ; let it be 

 recollected however, that these are casts of tlie animal 

 alone, and not of the valves of the shell, or of the opercu- 

 lum. If these exuvia be examined with care, a considerable 

 approach in the limbs and mouth to the more perfect 

 Crustacea will now readily occur, the former are composed 

 of six pair, in structure however, more resembling the limbs 

 of Mysis than the Decapoda, being divided into two 

 pluri-articulate branches from the second joint ; the moutli 

 is furnished as in the above tribe with two pair of true jaws 

 and with a palpigerous pair of mandibles, but is without 

 the pedimaxillffi, thus also they approximate in the 

 apparatus of the mouth to Mysis, and only difler in the 

 greater simplicity of the parts, and in the Palp being 

 composed of but two instead of three joints. A comparison 

 may be readily made by a reference to the Plates of Triton 

 and Mysis which mutually illustrate each other. 



The circumstance of their undergoing a metamorphosis 

 might have been urged against the Cirripedcs being Crus- 

 tacea, had not the author anticipated this objection by his 

 discovery, that these latter, contrary to the received opinion 



