276 



zooLoar. 



concealing the rudimentary antennse, and the feet 

 smaller, and eventually the bamacle-shape is attained. 



grow 

 The 



Fig. Si».— fapa of Lepas, macli en- 

 laiged. — After Darwlu. 



Fig. 227.— Nauplias of Salanus bal- 

 anoidu, mach enlarged. 



common barnacle (Balanus balanoides) attains its full size, 

 after becoming fixed, in one season, i. e., between the first of 

 April and November. 



Still lower than the genu- 

 ine barnacles are the root-bar- 

 nacles or Rhizocephcda, repre- 

 sented by Peltogaster (Fig. 

 329) and Sacculina (Fig. 2S0), 

 in which the young is a more 

 simple Nauplius fonn, like 

 the young of the Entomostra- 

 ca, while the adult is a sim- 

 ple sac, with a ganglion, but 

 no digestive organs. From 

 the feet of the young grow 

 out, after the animal becomes 

 sessile, long root -like fila^ 

 ments, which ramify in the 

 body of the crab, to which 

 these animals are firmly an- 

 chored. We can conceive of 

 no lower, more degraded Crus- 

 tacean than these root-barna- 



clee, the only signs of life being the powerful contractions 

 of the roots and an alternate expansion and contraction of 



Fig. 229. — Peliogatter mrvatvt, en- 

 larged 11 times, beneath the larva or Naa- 

 plins of Parthenopea, enlarged aboat 300 

 times.— From Bremu's Thietleben. 



