352 MALENTOZOA. CIRRIPEDIA. 



The Malentozoa, commonly known by the name of 

 Barnacles, are marine animals, which, until of late years, 

 were usually considered as Mollusca, but which a minute 

 examination of their structure shews to differ essentially 

 from that great series, and to approach more nearly to 

 the Entomozoa, or Articulata. They are, in fact, inter- 

 mediate between the two series, and may be placed with 

 either, or considered as a distinct group. They vary in 

 form, some being much compressed, others conical, con- 

 vex, or cylindrical. The body, which is soft, but more 

 or less articulated, curved, and placed with the back 

 beneath, and the hind part above, is enclosed in a thin 

 mantle, which is open only behind, and protected by a 

 kind of shell, composed of several pieces. The mouth, 

 situated at the lower end of the body, is furnished with 

 mandibles and maxillse, resembling those of certain Crus- 

 tacea. The head is not distinct, and there are no eyes 

 or tentacula. The abdominal face of the body is occu- 

 pied by two series of fleshy lobes, each bearing two long 

 curved horny appendages, formed of numerous joints, 

 and furnished with cilise or bristles. These organs, by 

 some named cirri, by others arms, or tentacula, appear 

 to be rudimentary limbs, and are constantly in motion, 

 now protruded from the sheath, then withdrawn, it being 

 apparently by means of them that the food is seized. 

 At the end of this series of organs is an elongated ovarian 

 tube, at the base of which is the intestinal aperture. 

 The heart is lodged in the dorsal part of the body, and 

 respiration is performed by branchiae placed at the base 

 of the lower cirri. The nervous system is a double series 

 of ganglia, as in the Crustacea, which they further re- 

 semble in their articulated limbs, and in other circuni- 



