^ 235. 



THE CEPHALOPODA. 



273 



covered by its anterior border.'^' The sea-water, which enters into the inte- 

 rior of the mantle, passes, with its various contents, into this funnel, and is 

 thence expelled through its anterior orifice. 



Many Cephalopoda have, on the dorsal wall of this organ directly behind 

 the anterior orifice, a tongue-shaped valve, which prevents the reflux of the 

 water. *^* 



With the Loligina, the sides of the trunk have variously-shaped cutaneous 

 lobes, which these animals use as fins.*'^' The Octopoda, on the other hand, 

 swim by rowing with their arras, which are bound together at their base by 

 a kind of natatory membrane, whose extremities have, each, a broader or 

 narrower cutaneous dilatation. '^> 



§ 235. 



The mantle of many of the Cephalopoda secretes a shell, which may 

 be either external or internal. 



1. An external shell is found with Argonauta and the Nautilina. That 

 of the Paper-Nautilus is very thin and flexible, — and, in its composition, 

 the organic base predominates above the calcareous matter, which consists 

 of thickly-set, small, round masses. The substance of the shell, which, with 

 Argo7iauta, is nowhere attached to the animal it encloses, is secreted prin- 

 cipally by the two large cutaneous lobes of the two median dorsal arras, 

 which lie upon the external surface of the shell. On this account, the 

 structure of the two surfaces of these lobes is difi'erent ; — the external sur- 

 face is quite smooth and has many chromatic cells ; while the internal has 

 scarce any of these last, but is covered with numerous reticulated, project- 

 ing lines, which become the more prominent when the lobes are contracted, 

 and between which, cell-like depressions are formed.*^' 



With the Nautilina, the shell has a very coraplicated structure ; its walls 

 are composed of two distinct layers, clearly separate, the internal of which 

 has a beautiful mother-of-pearl aspect. The cavity of the shell is divided, 

 even to the last spiral turns, by numerous transverse septa, which are all 

 perforated. With Nautilus,^'-^ a tube traverses the septa, while witli 



1 With Nautilus, the funnel is composed of two 

 pretty lar^^e, cutaneous lobes, placed ujjon both sides 

 of the throat, and reciprocally covering each other 

 on the ventral surface iu a cornet-like manner ; 

 see Owen, On the Nautilus, p. 10, PI. I. or Isis. p. 

 10, or Ann. d. Sc. Nat. loc. cit. p. 93, PI. I. III. 

 aud Valenciennes loc. cit. p. 2GJ, PI. X. fig. 1. 



2 This is so with Sepia, Sepiola, Lnligo, Se- 

 pioteuthis, Onychoteuthis, aud Nautilus.- For 

 this last, see Owen, loc. cit. PI. II. fig. 2, e., and 

 Valenciennes, loc. cit. PI. XI. fig. 4, /.. I have 

 sought for it in vain with Argonauta, Eledone, 

 aud Tremoctopus. It is alsi5 wanting with Loli- 

 gopsis aud Cranchia ; with Octopus, there e.Kists 

 in its place, that is, on tlie ventral surl'aoe of the 

 funnel, a transverse ridge. 



3 With Sepia, and Sepioteuthis, both sides of 

 the body are bordered their entire length with a 

 cutaneous lobe. With Loligo, and Onychoteutliis, 

 the two fins are triangular and inserted on the 

 posterior extremity of the body ; they are round 

 and sliort with Sepiola, Loligopsis, and Cranch- 

 ia ; in the first of these genera, they are situated 

 on the middle of the sides of the body, aud in the 

 last two, upon its extremity. 



4 These interbranchial natatory membranes ex- 

 ist with Octopus, Eledone, iiml Tremoctopus ; 

 they are particularly developed in this last genus, 

 between the two pairs of dorsal arms. 



In this same genus, as also with Argonauta, tlr^: 

 two dorsal arms are terminated by a very large 

 cutaneous lobe, and are used not only as locomo- 

 tive organs, but also for keeping the shell iu place 

 by being applied on its external surface ; see Fe- 

 russac, loc. cit. Argonauta, PI. I. fig. 5, 6, PI. VI. 

 fig. 2, aud in the Mem. de la Soc. d'Hist. Nat. de 

 Paris, II. 1S25, p. 160, PI. VI. fig. 2, or Isis, 1832, 

 p. 460, Taf. V. fig. 2 ; Rang, Docmu. pour servir 

 A I'llist. nat. des Cephalopodes, in the Magaz. 

 de Zool. 1837, Livr. IV. p. 19, PI. LXXXVI.- 

 LXXXVIII., or Ann. d. Sc. Nat. A'll. 1837, p. 

 176 ; and Delle Chiaje, Descriz. loc. cit. Tav. VII. 

 fig. 1, 2. 



1 It has been attested by several observers, that 

 these two cutaneous lobes furnish the substance of 

 the shell, aud that, also, with which the animal re- 

 pairs accidental lesions ; see Rang, llagaz. de 

 Zool. loc. cit.; Jeanette Power, in the Atti dell' 

 Acad, di Scienz. Nat. di Catania, XII. 183'J. 

 or Isis. 1845, p. 606, or in fViegmann's Arch. 

 1845, 1, p. 369 ; and, Further experiments and ob- 

 serv. on the Argonauta Argo, in the Reports of 

 the Brit. Assoc. 1844, Notices and Comnmnic. p. 

 74. For the non-parasitism of the anunal, see, 

 moi'eover, Van Beneden, loc. cit. p. 4, aud Ferus- 

 sac, loc. cit. p. 114. 



- Ve BLainville, in the Nouv. Ann. du MuseniM 

 d'Hist. Nat. HI. 1834, p. 3, PI. I. II. 



