CIRRIPEDIA 



341 



fixed by the discs on its antennules, and its body rotates within the 

 shell, so that the ventral surface is directed backwards (Fig. 245 

 A, B). Now the shell and body are rotated upwards on the antennae 

 so that the adult position is assumed (Fig. 245 C) ; meanwhile the shell 

 plates appear, the preoral region elongates to form the peduncle, and 

 the abdomen disappears. 



Scalpellum (Fig. 246 C, D) attaches itself to fixed objects, usually in 

 deep waters . It diff'ers from Lepas in possessing a number of additional 

 plates on the capitulum, and scales of a similar nature on the peduncle . It 

 is more remarkable in possessing what are known as com/)/ewe«^<2/m<2/^^. 



al. ^' 



>cu. 



Ih. M. e.' e. 



Fig. 245. Diagrams of three stages in the metamorphosis of Lepas. From 

 Korschelt and Heider. A, The Cypris stage. B, The attached larva (pupa). 

 C, The young Lepas. ab. abdomen; al. alimentary canal; an.' antennule; 

 car. cuticle of carapace of larva, not yet shed; cna. carina; e. compound 

 eye; e.' median eye; M. mouth; scu. scutum; tgm. tergum; th. thoracic 

 limbs; x. origin of carapace fold; y. a ventral fold of the head. 



A few species of the genus are composed entirely of hermaphrodites 

 as Lepas is. In most, however, some individuals are without female 

 organs. These individuals are always smaller than those which 

 possess ovaries, and live within, or at the opening of, the mantle cavity 

 of the latter. In some species they almost perfectly resemble these in 

 organization, but usually they are more or less degenerate, being 

 sometimes even without an alimentary canal. As a rule the more de- 

 generate live within the mantle cavity of the partner, the less 

 degenerate on its mantle edge. In certain species, which have very 



