SECT. vm. 



CIRR1PEDIA. 



215 



the filaments uncurled ; then, as they close again, the in- 

 numerable hairs meet and form a sieve through which 

 the water escapes, but whatever minute particles it may 

 contain are inextricably entangled, and when the small 

 animals fit for food have been selected, the filaments 

 curl inwards, and carry them to the mouth ; there they 

 are seized by the jaws and sent through a short gullet to 

 be digested. 



The feet and cirri are moved by very strong muscles, 

 the valves of the lid are opened and shut by muscles at- 

 tached to the mouth of the shell ; and when the animal 

 wishes to protrude its cirrhated feet, the longitudinal 

 muscles attached to the lid come into action, and it 

 draws itself in again by short muscles attached to the 

 base. All the organs of the animal are supplied with 

 nerves by a double nerve-centre in the head, and a circle 

 of nerve-centres round the gullet. The ears are situated 

 at the base of the first pair of cirrhated 

 feet, and consist of a cavity enclosing a 

 vesicle closed by a nerve, and contain- 

 ing a liquid, but no otolites. 



The common Lepas anatifera, of 

 which fig. 155 is a section, as well 

 as its allies, have a thick stem and a 

 conical shell closed on the back, but 

 gaping in front. Their internal struc- 

 ture does not differ essentially from 

 that of the Balanidse, and it has been 

 proved by Mr. J. V. Thompson and 

 others, that there is no material dif- 

 ference between their transformations 

 during the early stages of their lives. 



Each individual cirriped is both male 

 and female, and the eggs are hatched before they 

 come into the water. Mr. Gosse mentions that he had 

 seen the Balanus porcatus throw out a dense column 



Fig. 155. Section of 

 Lepas anatifera. 



