IV PEDUNCULATA—OPERCULATA 89 
which they live; they exhibit a degenerate structure, but. still 
retain two pairs of cirri. The large individuals of /. guadrivalvis, 
on the other hand, are hermaphrodites, but they harbour within 
their mantles minute complemental males similar to those of 
L. cumingvi, 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, Se/ache 
maxima and Spinawz 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 the 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 Rhizo- 
cephala, which, as will be shown, 
derive their nutriment from a 
system of roots penetrating the R--- 
host and growing out from what 
corresponds morphologically to the 
peduncle. 
R.L L wie 
Sub-Order 2. Operculata. 
Fic. 60.—Diagram of the shell of an 
Operculate Cirripede. a “ Ala,” or 
The “ acorn-barnacles ” appear overlapped portion of a ‘‘ compart- 
; se - BH oe ment 3-8, basis; C cara; (CLL, 
later in geological time than the — carino-tateral; L, lateral: 2, ros. 
earlier stalked forms. Verruca and trum; », “radius,” or coe 
- : - ortion of a compartment; A.L 
Chthamalus are found in the Chalk, ate ea (After DEL 
and survive down to the present 
day, but Balanus does not occur until middle Tertiary times. 
Representatives of the last-named genus are familar to every one, 
