578 



ZOOL( )GY 



bivalvcd carapace, fonued by a fold of the skin, and strengthened 

 by five calcareous plates. Of these one is median and dorsal, and 

 is called the carina (c); two are lateral and proximal, the scuta (s); 

 and two lateral and distal, the tcrga (t). During life the carapace 

 is partly open, and from the ventrally placed aperture delicate 

 setose filaments are protruded and keep up a constant grasping 

 movement : these are the endo- and exopodites of the biramous 

 thoracic feet, of which there are six pairs. Removal of the carapace 

 shows the feet to arise from a vermiform unsegmented body 

 (B), attached on the ventral aspect to the stalk and carapace by 



Fig. 454— lepas anatifera. A, the outire animal; B, anatomy, ui, antonnule ; c. carnia ; 

 cd. cement-gland ; I. digestive gland ; i«. adductor muscle ; od. oviduct ; oa. ovary ; p. (ui B) 

 yenis and (in A) peduncle ; s. scutum ; (. tcrguni and testis ; ml. vas deferens. (From Langs 

 CoiiiiMnUii>t Anaiiiiiiij, after Darwin and Glaus.) 



its anterior end, while its posterior end is free and terminates in 

 a long filament, the penis (p), immediately dorsal to which is the 

 anus. The mouth is ventral and anterior, and is provided with ■ 

 a pair of mandibles and two pairs of maxillte. There are no 

 antennae : at first sight the antennules appear to be absent, but 

 a careful examination shows the presence of a pair of minute 

 structures {a) on the proximal or attached surface of the stalk, 

 and embedded in the cement by which the animal is fixecl to its 

 support ; these are the antennules, and their position relatively to 

 the mandibles shows that the stalk is formed by an elongation of 

 the anterior region of the head. 



