

CIRRHOPODA. 



687 



is open, and of little less diameter than the 

 upper part, which led Dufresne to conclude 

 that the animal does not form a shell until it 

 be considerably advanced in growth. This 

 seems to be very probable, as the base is im- 

 bedded deeply in the integument of the Whale, 

 and descends lower the more it increases in 

 size, so as to leave only the summit of the 

 shell visible. The imbedded portion is gene- 

 rally deeply coloured by the tegumentary pig- 

 ment of the Whale. In coronula, which also 

 inhabits the backs of Whales, but has the same 

 general structure of shell as the majority of 

 Balanids, the valves are deeply partitioned, 

 and provided with toothed processes, fitted to 

 fix the animal in its site. 



The only other calcareous coverings that re- 

 main to be noticed are the rudimentary valves 

 in Otion and Cineras, animals that bear a 

 general resemblance in form to Anatija, but 

 which are covered chiefly by a semicartila- 

 ginous tunic. There are two small valves in 

 Otion, which are attached to the anterior as- 

 pect just above the brachial orifice. In Cine- 

 ras they are five in number, two in the same 

 situation as those of Otion, two along the ter- 

 minal margin of the outer tunic, and one 

 unpaired along the dorsal aspect. These are 

 imbedded by their margins in the semi-carti- 

 laginous tunic, and seem to be formed by it ; 

 calcareous matter being added to their margins 

 in successive layers. 



The ligamentous membrane, by which the 

 valves in Anatifa are connected one with the 

 other and with the peduncle, is strong but 

 pliant. It is an extension of the outer cover- 

 ing of the peduncle. At the brachial orifice, 

 it is reflected inwards to join the mantle. In 

 addition to this, each valve has a membrane 

 of its own, which closely invests its inner sur- 

 face, and is not continuous with those of the 

 other valves. The peduncle of this and the 

 allied genera may be considered as a kind of 

 developed ligament. If we regard the upper 

 pair of valves as analogous to the valves of 

 Acephalous Mollusca, the peduncle is found 

 to be attached to them at points corresponding 

 to the situation of the ligament in those shells. 

 This organ is sometimes of great size. In the 

 British seas it occasionally occurs two feet in 

 length. Its epidermis is generally rough, 

 wrinkled transversely, coriaceous, and elastic : 

 Otion, however, has it very smooth and stiff, 

 nearly cartilaginous, diaphanous. In some 

 species it is so elastic as to admit of exten- 

 sive lateral motion, and much elongation and 

 contraction. These movements are effected by 

 a layer of strong muscular tissue beneath the 

 skin, within which there is a large organ, 

 granular in its structure, regarded by some 

 anatomists as the ovary. Burmeister is of 

 opinion that the peduncle is merely an organ 

 of support : and he suggests that the granular 

 parenchymatous mass, which fills its interior, 

 is destined solely for its own nutrition, which he 

 seems to think is independent of the other parts 

 of the animal. In most species, it is by its epider- 

 mis that the peduncle adheres . The peduncle pre- 



sents still other varieties than those just mention- 

 ed. Po/licipcx villusus has it covered partly with 

 imbricated scales, and partly with a hairy coat ; 

 and Pollicipes quudrivalvis has its valves wholly 

 encased in a large prolongation of the pe- 

 duncle, which, on its upper surface, bears 

 four valves arranged nearly in the same way 

 as those of the opercule of the Balanids. The 

 base of Coronula is closed by a strong fibrous 

 membrane connected with the body of the 

 animal only by a process of the epidermis. 

 It is regarded by Burmeister as the analogue 

 of the peduncle of the Lepads. 



The cartilaginous tunic of Otion Cuvieri, 

 at its summit, is enlarged into two large auri- 

 form appendages, hollow, having a crescentic 

 orifice externally, and internally commu- 

 nicating with the visceral cavity of the animal ; 

 no organ is discoverable within them, but 

 their cavities receive the terminations of a duct, 

 which descends on the dorsal aspect of the 

 body, in the groove of the dorsal valve, from 

 the peduncle. 



Of the mantle, as one of the tegumentary 

 organs of the Cirripeds, little more need be 

 said, than that it is generally a very thin trans- 

 parent membranous sac, surrounding the vis- 

 ceral mass, open only at the brachial orifice, 

 where it joins the epidermis and intervalvular 

 ligament, and is reflected so as to form an 

 inner lining for the visceral cavity. It has 

 neither fringes of filaments, nor foliated pro- 

 cesses. M. St. Ange describes another tunic 

 of the visceral mass, which, he says, is con- 

 tinuous with the horny covering of the arms. 



Locomotion. Their base being permanently 

 fixed, the principal motions of the Cirripeds 

 are those of the arms, which seem to be sub- 

 servient at once to the respiratory and to the 

 digestive functions. But, as has just been 

 mentioned above, the peduncle of Anatifa and 

 other allied genera is moved both laterally and 

 in the way of contraction and extension, and 

 the valves, in the same animals, are so moved 

 as to open and close the brachial orifice. ' The 

 motions of the arms are, in many species, 

 very rapid, and are performed with great re- 

 gularity ; proving the existence of a complete 

 muscular apparatus both at their bases and 

 within their numerous joints ; but the parts are 

 too minute to admit of a satisfactory examina- 

 tion being made of their structure. The Lepads 

 have a strong transverse adductor muscle placed 

 between their superior valves, just above the 

 brachial orifice (a, fig. 340) ; this muscle seems 

 to be every way analogous to the same organ 

 in Acephala. Its action closes the brachial 

 slit very accurately ; while its relaxation admits 

 of its being opened by the advance of the 

 arms grouped together into the form of a wedge. 

 This movement of the arms cannot be per- 

 formed without the whole body being carried 

 outwards ; which is effected apparently by the 

 contraction of certain delicate muscular fibres 

 spread over the mantle, and attached around 

 the margin of the orifice. Cuvier describes a 

 similar set of fibres, " attached to the mantle 

 opposite the insertion of the peduncle, by 



