276 



ZOOLOGY. 



concealing the rudimentary antennae, and the feet 

 smaller, and eventually the barnacle-shape is attained. 



grow 

 The 



Fig. 228.— Pupa of Lepas, much en- 

 larged.— After Darwin. 



Pig. 227 ^Nauplius of Balanue bal- 



arvoidtt, much 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 RMzocephala, repre- 

 sented by Peltogaster (Fig. 

 339) and Sacculina (Pig. 230), 

 in which the joung is a more 

 simple Nauplius form, like 

 the young of the Entomostra- 

 ca, while the adult is a sim- 

 ple sac, containing no diges- 

 tive organs or nerves. 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- 



cIps, the only signs of life being the powerful contractions 

 of the roots and an alternate expansion and contraction of 



Fie. 229. — Peltogaster curvafus, en- 

 l»ro;ed li times, beneatli the larva or Nau- 

 pliiiB of Parthenopea, enlarged about 2Q0 

 times.— From Brenm'a Thierleben. 



