SECT. VHI 



CIRR1PEDIA. 



213 



SECTION vni. 



CIRBIPEDIA. 



THE metamorplioses of the Cirripeds, and their resem- 

 blance to the lower Crustacea at each moult, are still 

 more remarkable than those of the Epizoa. They form 

 two primary groups, the Balanidse, or Acorn shells, and 

 the Barnacles or Lepadidse, which have peduncles or 

 stalks. Both are parasites, but they do not draw their 

 sustenance from the substances they adhere to. 



The Balanidse (fig. 153) are grouped in innumerable 

 multitudes, crowded together on the rocks of the southern 

 and western coasts of England, like 

 brown acorns. They have an ob- 

 scurely articulated body, enclosed 

 in a membrane, and defended by a 

 multivalve conical shell. The base 

 of the shell is a broad disk fixed to 

 a foreign substance by a cement 

 secreted by the animal. The walls 

 consist of twelve triangular com- 

 partments. Six rise upright from Fig-153 . ^^ cnlcatns . 

 the edge of the disk, and end in a 

 point at the open margin of the shell ; the other six are 

 inverted and wedged into the interstices. The whole 

 cone thus constructed is divided into from four to eight 

 pieces by expansive seams. The mouth of the cone is 

 closed by a lid formed of four triangular valves, which 

 meet in a point in the centre, and shut in the creature. 



