276 



ZOOLOGY. 



concealing the rudimentary antennas, and the feet grow 

 smaller, and eventually the barnacle-shape is attained. The 



Fig. a^o.-Hupa of Lepas, much en- 

 larged. After Darwin. 



Fig. 227. Nauplius of Balanus bal- 

 anoidet, 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 Rhizocephala, repre- 

 sented by Peltogaster (Fig. 

 229) and Sacculina (Fig. 230), 

 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, 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 

 uiese animals are firmly an- 



, Fiff. 229. Peltogaster curvatiit, en- 



Chored. \Ve Can Conceive Of larged 14 times, beneath the larva or Nau- 



i j -i r\ plius of Parthenopea, enlarged al>out 200 



HO lower, more degraded OrUS- times. From Brehm's 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 



