578 



ZOOLOGY 



SECT. 



bivalvcd carapace, formed 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 terga (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 



U. 



FIG. 454. Lepas anatifera. A, the entire animal; B, anatomy, wj, antennule ; c. carina ; 

 cd. cement-gland ; 1. digestive gland ; m. adductor muscle ; od. oviduct ; ov. ovary ; p. (111 B) 

 penis and (in A) peduncle ; s. scutum ; t. tergum and testis ; vd. vas defereiis. (From Lang's 

 Comparative Anatomy, 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, an x d is provided with 

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

 antenna: 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 fixed 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. 



