PEDUNCULATA OPERCULATA 



89 



which they live ; they exhibit a degenerate structure, but still 

 retain two pairs of cirri. The large individuals of /. q-ioadrivalvis, 

 on the other hand, are hermaphrodites, but they harbour within 

 their mantles minute complemental males similar to those of 

 I. cumingii, though they are rather larger. 



Fam. 4. Anaspidae. — This includes the remaining pedun- 

 culate genera, characterised by the fleshy nature of the 

 mantle and peduncle, which are both entirely devoid of cal- 

 cifications. The species of Alepas live upon Echinoderms and 

 various other animals ; Chaetolepas upon Sertularia, and 

 Gymnolepas upon Medusae. Anelasma squalicola is an interesting 

 form, living parasitically upon the Elasmobranch fishes, Selache 

 maxima and Spinax niger in the North Sea. The peduncle is 

 deeply buried in the flesh of the host, so that only a portion of 

 the dark blue capitulum protrudes to the surface. From the 

 whole surface of the peduncle a system of branching processes is 

 given off, which ramify far into the tissues of the fish, and 

 communicate inside the peduncle with the lacunar tissue, which 

 is packed round all the organs of the Cirripede. There can be 

 small doubt that tlie Anelasma derives its nutriment parasitically 

 through this root-system, since the cirri are mere fleshy lobes un- 

 adapted to securing food, and the alimentary canal is always 

 empty. This animal has a sug- 

 gestive bearing on the Ehizo- 

 cephala, which, as will be shown, 

 derive their nutriment from a 

 system of roots penetrating the 

 host and growing out from what 

 corresponds morphologically to the 

 peduncle. 



R- 



B- 



R.L 



CL 



Sub-Order 2. Operculata. 



The " acorn-barnacles " .appear 

 later in geological time than the 

 earlier stalked forms. Verruca and 

 C'hthamalus are found in the Chalk, 

 and survive down to the present 

 day, but Balanus does not occur 



Fig. 60. — Diagram of the shell of an 

 OiJerculate CirripeJe. a "Ala," or 

 overlapped portion of a "compart- 

 ment " ; B, basis ; C, carina ; CL, 

 carino-lateral ; L, lateral ; R, ros- 

 trum ; r, "radius," or overlapping 

 portion of a compartment ; R.L, 

 rostro-lateral. (After Darwin.) 



until middle Tertiary times. 



Eepresentatives of the last-named genus are familiar to every one. 



