/. CRUSTACEA: CIRlilPEDIA. 



423 



The antenna?, the first simple, the second frequently two- 

 branched, are used for swimming and creeping, and are bent back- 

 wards and provided with numerous joints and hairs. The 

 following appendages (mandible, maxillfe, and three pairs of legs) 



Fig. 426. — Ct/pris fasciatus, adult female. (After Glaus.) I-IV^ appendapces; c, furca; 

 e, eye; /, liver; rn, adductor muscle of shell; o, ovary; s, shell ^land. 



vary greatly from genus to genus. The internal structure is also 

 variable. The Ostracoda are largely bottom forms and live in fresh 

 and brackish water as well as in the sea. 



Cypridinid^e. First two pairs of legs maxillary in character, the hist 

 developed into a hook for cleansing the shell; heart present; marine. 

 Cypridina* Cypridid.e. First pair of legs maxillary in character ; 

 heart lacking; fresh water. CyjJjis,- C'atidoha* 



iSnb Class V. C'irripedia. 



The cirripeds, or barnacles, differ from all other Crustacea in 

 that they have lost their locomotor p)Owers and live attached to 

 rocks, floating timber, and the like. In some cases they attach 

 themselves to other animals, as crabs and molluscs, or, as in the 

 case of Coromila, to whales. This leads ^ ,f 



in Anelasma and the Ilhizocephala to a 

 true parasitism, the liarnacle not only 

 attaching itself to an animal but sucking 

 its juices as food. 



'J'he attachment is by tlio dorsal sur- 

 face in the neighborliood of the head, 

 and is initiated by the first antennae, in 



which is a cement gland secreting a fig. 427.-iv,;a»».Wiom,.r/,*acor7i 

 rapidly hardening cement. The region "SS^^i ^^^^S^^^Z 

 of fixation in the lialanida? (fig. 427) ;:^™liSm 'V/t^cSta""; ^nl 

 lies in the plane of the head; in the ^^'^^'^ '"■ 

 Lepadida? it is drawn out into a long muscular stalk (fig. 114). 

 To this attached life are related all the peculiarities of structure. 



