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MANUAL OF ZOOLOGY. 



of forked, cirrated limbs, which are attached to the thorax, and 

 serve to provide the animal with food. The two more import- 

 ant types of the Cirripedia are the Acorn-shells (Balanida) 

 and the Barnacles (Lepadidce). In the former the animal is 

 sessile, the larval antennae, through which the cement exudes, 

 being embedded in the centre of the membranous or calcareous 

 " basis " of the shell. In the latter the animal is stalked, and 

 consists of a " peduncle " and a " capitulum." The peduncle 

 consists of the anterior extremity of the body, with the larval 

 antennae, usually cemented to some foreign body. The capit- 

 ulum is supported upon the peduncle, and consists of a case 

 composed of several calcareous plates, united by a membrane, 

 enclosing the remainder of the animal. 



As regards the development of the Cirripedia, the larva has the form of 

 a "Nauplius" (fig. 143, A), with an unsegmented, pyriform body, a median 

 eye, and a dorsal carapace. During its life as a Nauplius, the young moults 

 several times (seven times in Lepas fascicularis, which is here taken as ex- 

 emplifying the development of the Cirripedia in general) ; and these various 

 castings of its integuments are accompanied with material changes of form. 



Fig. 143. Development of Lepas fascicula ris. A, Early stage of the Nauplius, show- 

 ing the three pairs of appendages, of which the hinder two pairs are bifurcate : o Eye- 

 spot ; b Labrum ; g Gullet ; h h Lateral horns. B, the free-swimming Cypris-stage or 

 "pupa," after the sixth moult, the antennae and feet retracted within the shell : an 

 Antenna, with its suctorial disc, traversed by the duct of the cement-gland (eg ) ; 

 sg Shell-gland ; o Eye ; ad Adductor-muscle ; / Feet ; c Caudal process. Both 

 figures are greatly enlarged. (After Von Willemoes-Suhm.) 



When fully grown, the Nauplius has an oval or pyriform body, enclosed in a 

 carapace, provided with long caudal and dorsal spines. There are three pairs 

 of limbs, of which the first pair (representing the antennae) are undivided, 

 while the two hinder pairs (fig. 143) are bifid, and all carry natatory 

 bristles. There is a very large labrum (fig. 143, b} placed in front of the 



