296 



ZOOLOGY. 



concealing the rudimentary antennae, and the feet 

 smaller, and eventually the barnacle-shape is attained. 



grow 

 The 



Fig. 233. Pupa of Lepas t much en- 

 larged. After Darwin. 



Pig. 233. Nauplius of Bcdanus bcit- 

 noicles, 



much enlarged. 



common barnacle (Balanus balanoides) attains its full size, 

 after becoming fixed, in one season, i. e. 9 between the first of 

 April and November. 



Still lower than the genu- 

 ine barnacles are the root-bar- 

 nacles or Rhizocephala, repre- 

 sented by Peltogaster (Fig. 

 234) and Sacculina (Fig. 235), 

 in which the young 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- times.-From BreWs Thierleben. 



tacean than these root-barna- 

 cles, the only signs of life being the powerful contractions 

 of the roots and an alternate expansion and contraction of 



Fig. 234. Peltogaster curvatiis, en- 

 larged li times, beneath the larva or Nau- 

 plius of Parthenopea, enlarged about 200 



