65 



OCTOPODA. 



OCTOPODA. 



conclusion in favour of the animal beins; the coustructor of the shell 

 and consequently against the parasitic theory, from observations mad< 

 by him on A rgonauta hians. 



In 1837, M. Rang, on his return from Algiers, where he had been 

 observing these animals, had an interview with M. De Blainville, who 

 had then the observations which Madame Power had just made in his 

 hands ; and, in April of th.it year, M. De Blainville read his elaborate 

 Report, and afterwards published it, with additional dissertations, in 

 the form of a memoir or letter, in the third number of the ' Annalef 

 Fran9aises et Etrangeres d'Anatomie et de Physiologic.' His argu 

 ments in favour of parasitism appear to be based on the following 

 <lata : 1, That the name species of Cephalopod is not always found it 

 the same sneuies of shell 2, That the natural position of the anima 

 in the shell varies, the back of the animal being sometimes next the 

 outer wall of the shell, sometimes next the involuted spire. 3, That 

 the animal does not occupy the posterior part of the shell. 4, That the 

 form of the animal and of its parts offers no concordance or analogy 

 with the shell. 5, That the shell is too opaque to have permitted the 

 influence of light in the development of the coloured pigment in the 

 mantle of the cephalopod of the Argonaut. 6, That it is very far 

 t'rorn being true that the argonaut-shell possesses the flexibility and 

 elasticity requisite to harmonise with the locomotive and respiratory 

 movement* of the animal. 7, That the animal suffers no appearance 

 of inconvenience when deprived of its shell. 8, That a cephalopod 

 has been discovered in the Sicilian seas like that which inhabits the 

 Argonaut, but without a shell. These data are designated by Pro- 

 fessor Owen, to whose observations we shall presently advert, as false 

 facts, with the exception of the third, which a only partially false, 

 being true when stated with reference to the more mature animal only. 

 The other arguments of M. De Blainville are noticed by Professor 

 Owen as founded on undoubted or admissible facto; but the Professor 

 denies the conclusion drawn by M. De Blainville. 



M. Sander Rang in consequence of the appearance of M. De Blain- 

 ville's memoir or letter, published in Guerin's ' Magasin de Zoologie ' 

 a very interesting paper under the title of ' Documents pour servir a 

 1'Hi.ttoire Naturelle des Cephalopods Cryptodibranches.' In this 

 memoir M. Rang's observations are confirmatory 1, of Madame 

 Power's statement that the siphon is applied to the part of the shell 

 opposite the involuted spire ; 2, of the accuracy of her description of 

 the relative position of the so-called sails of the Argonaut with refer- 

 ence to the shell ; 3, of her discovery of the faculty possessed by the 

 animal of repairing the shell, and many other points. 



No one will refuse to M. Rang the acknowledgment that he is not 

 only a very accurate observer, but that he is well versed in the natural 

 history and anatomy of the Mollutca generally ; so that here at least 

 no doubt can be thrown on the observations. 



In February, 1839, a highly interesting and valuable series of speci- 

 mens of the Paper Nautilus (Argisttauta Argo) consisting of the 

 animals and their shells of various sizes, of ova in various stages of 

 development, and of fractured shells in different stages of reparation, 

 were exhibited to the Zoological Society of London, and commented 

 on by Professor Owen, to whom they had been transmitted for that 

 purpose by Madame Power, who had formed the collection in Sicily, 

 138. In the course of his comments the Professor went at large 

 into the subject, and in addition to the observations above alluded to 

 with regard to the alleged false facts and admissible facts whereon M. 

 De Blaiuville had founded his reasoning, combated at great length, 

 and, in our opinion, with signal success, the arguments of those who 

 adhered to what may be termed the parasitic opinion ; and recapitulated 

 as follows the evidence which, independently of any preconceived theory 

 or statement, could be deduced from the specimens then on the table. 



1. The cephalopod of the Argonaut constantly maintains the same 

 relative position in its shell 



2. The young cephalopod manifests the same concordance between 



.i-m of its body and that of the shell, and the same perfect 

 adaptation of the one to the other as do the young of other testaceous 

 molluscs. 



3. The young cephalopod entirely fills the cavity of its shell; the 

 faadtu of the sac begins to be withdrawn from the apex of the shell 

 only when the ovarium begins to enlarge under the sexual stimulus. 



The shell of the Argonaut corresponds in eize with that of its 

 inhabitant, whatever be the differences of the latter in that respect. 

 (The observations of Poli, of Prevoat, of King, and of Owen, are to 

 the same effect.) 



i. The shell of the Argonaut possesses all the requisite flexibility 

 and elasticity which the mechanism of respiration and locomotion in 

 the inhabitant requires ; it is also permeable to light. 



6. The cephalopod inhabiting the Argonaut repairs the fractures of 

 its shell with a material having the same chemical composition as the 

 il shell, and differing in mechanical properties only in being a 

 little morn opaque. 



The repairing material is laid on from without the shell, as it 

 should bo according to the theory of the function of the membranous 

 arms as calcifying organs. 



, When the embryo of the Argonaut has reached an advanced stage 

 of development in ovo, neither the membranous arms nor shell are 



i.e shell of the Argonaut does not present any denned nucleus. 



SAT. HIST. DIV. YOU IV. 



Professor Owen concluded a most elaborate commentary by stating 

 that he regarded the facts already ascertained to be decisive in proof 

 that the cephalopod was the true fabricator of the shell; and thus, in 

 our opinion, is set at rest principally by the experiments of Madame 

 Power a question which had divided the opinions of zoologists from 

 the time of Aristotle, who left the subject with the following acknow- 

 ledgment : " But as touching the generation and growth of the shell 

 nothing is as yet exactly determined." * 



M. Rang's account of the locomotion of Argonauta Argo is most 

 interesting. When the animal was at rest, and contracted within its 

 shell,' it exhibited the appearance figured below. 



Argonauta Argo contracted within its shell, and the membrane of the sail- 

 arms partially covering it.- The eggs were never seen by M. Rang in the place 

 where they are represented, but much more within the opening. (Rang.) 



" To return to the description of our poulp," says M. Rang, " which 

 we left contracted within the argonaut-shell, and watching with an 

 attentive eye what took place around it, we saw it extending itself 

 from out its shell, and protruding six of its arms ; then it threw itself 

 into violent motion, and travelled over the basin in all directions, often 

 dashing itself against the sides. In these different movements the 

 body leant a little towards the anterior part of the shell ; ami the long 

 slender arms, very much extended and collected into a close bundle 

 were carried before it, as well as the tube, which showed itself open 

 and protruded. The locomotion was effected in the ordinary manner 

 of poulps. the movement being backwards by means of the contraction 

 of the sac and the expulsion of water through the siphon. The dis- 

 position of the animal and shell is the most favourable for accelerating 

 the motion of the creature. The lightness of the shell ; its narrow 

 and keeled form ; its width, which is smallest at the part presented 

 first for cleaving the water ; the membrane smoothing over all inequa- 

 lities of the shell ; the bundle of arms extending behind so as to offe> - 

 the least possible resistance ; the two arms stretched like a bridge over 

 the cavity where the eggs are, as if to throw off the water from that 

 cavity; all these adaptations concur to facilitate the glHiug of the 

 animal through the medium in which it is to move." 



M. Rang thought that he perceived in the movements of the animal, 

 when in open water, that it had its back uppermost, and consequently 

 the tube below, but he did not constantly see it so ; he observed it 

 however with more certainty in specimens of poulps whose arms had 

 been deprived of their membranes. 



The animal which they had been watching, as above described, 

 'aligned by its efforts in a confined space, and perhaps injured by tho 

 shocks which it had sustained in coming in contact with the side of 

 ;he basin, allowed itself to sink to the bottom, and half contracted 

 itself in order to take repose ; soon after which it exhibited another 

 and unexpected spectacle. Fixing some of the acetabula of its fore 

 arms upon the bottom of the basin, it erected itself upou its head, 

 spreading out its disc, and carrying the shell straight above it in the 

 normal position of tho shells of gastropods ; then, beginning to crawl, 

 t presented the appearance of a pectinibranchiate mollusc, as M. Rang 

 lad remarked in the note to the Academy of Sciences. Half drawn 

 Kick into its shell, the animal appeared to crawl upon its disc, tho 

 >almatures of which were a little raised to follow the movements of 

 ts arms. The body was hidden in the shell ; the siphon, placed in tho 

 anterior part of it, was turned forwards ; the arms which were at 

 iberty were very much protruded and twisting round, two before and 

 ,wo on each side ; the base of the two large arms seemed to prolong 

 backwards the locomotive surface, and then rising along the keel they 

 again covered it with their large membranes, as when the poulp was 

 wimming in deep water. " Thus," continues M. Rang, " this mollusc, 

 it once pelagic and littoral, presents a most singular anomaly ; when 

 t swims at the surface of the water having its ventral part lowermost 



' Hist. Anim.,' ix. 37 ; where a detailed account of the locomotion of tho 

 Nautilus, iU tailing, &c., is given. 



