IV 



FAMILIES OF PEDUNCULATA 



than bags of spermatozoa, but they possess to varying degrees 

 the ordinary organs of the adult in a reduced condition. The 

 male of tf.jirronii (Fig. 55, A) retains the shape and skeletal plates 

 of the ordinary form, and differs chietly in its reduced size; but 

 the more common condition is exhibited by the male of S. 

 nilijure (Fig. 52, A), where the scutes are reduced to vestiges 

 round the mantle-opening, and almost the whole of the bod}- is 

 occupied by the greatly developed generative organs. (.">) In 

 a few species, e.g. S. I'dutinum and >S. or/n/f /////, the individuals 

 are purely dioecious, being either females of the ordinary 

 structure resembling the hermaphrodites of the other Lepadidae, 

 or dwarfed males resembling closely the complemental males 

 described above for S. rnl<jri'. 



The nature and derivation of these various conditions will be 

 discussed when the parallel cases found in T 



//>/" and among the IJhizocephala have 

 been described. 



The remaining genus of the Polyas- 

 pidae, also characterised by the presence of 

 numerous skeletal plates on the capitulum, 

 is LitJiotrya (Fig. 56), which bores into 

 rocks and shells, and is an inhabitant of 

 the warm and tropical seas. 



Tin- pi'dunele of the full-grown animal 

 is completely imbedded in the rock or shell 

 to which it is attached, and at the basal 

 end of the peduncle is situated a cup com- 

 posed of large irregular c.alcilied pieces. 

 This cup is, however, not formed until the 

 animal has ceased to burrow. The exca\a- 

 lion of the subslral urn is effected by means 

 of a number of small rasping plates which 



COVer the peduncle, the whole being set ill 



motion by the peduncular muscles. 



Fam. 2. Pentaspidae. Tn this family 



an; placed a number of genera., and among I hem the common 

 Lepct, the Species of which possess typically live skeletal plates, 

 viz., a earina and a pair of scuta and of terga. I he peduncle being 

 naked. These forms are a later development of Cirripede evolu- 

 tion, and did not come into existence till Terti;ii\ limes. Some 





cup : (', cavina ; /,'. i o 

 triini ; X, sriilnin ; '/', 

 tergum. (After I >.n win. ) 



