PROF. OWEN ON THE ARGONAUT. 427 



was impossible to doubt but that the reparation, as well as the subsequent 

 growth, had been the effeets of the same agent. The repaired parts of the 

 shell re-acted precisely like the ordinary shell with nitric acid. 



" Mr. Owen then observed that the specimens submitted to the meeting 

 by Madame Power, possessed in themselves the means of confirming or 

 refuting her theory of the formative organs of the shell of the argonaut ; 

 for if the shell were secreted, as in gasteropods &c, by the edge of the man- 

 tle covering the body, the new material by which the breaches of the shell 

 had been repaired, should have been deposited on the inside of the frac- 

 tured edge ; but, on the contrary, it was clearly obvious in two of the spe- 

 cimens, that the new material had been laid on upon the outside of the 

 fractured part — as it must have been, supposing the vela or membranous 

 arms to be the calcifying organs. 



" Mr. Owen then recapitulated, as follows, the evidence which, indepen- 

 dently of any preconceived theory or statement, could be deduced from the 

 admirable collection of Argonauta Argo, due to the labours of the accom- 

 plished lady who had contributed so materially to the elucidation of a prob- 

 lem which had divided the zoological world from the time of Aristotle. 



" 1st. The cephalopod of the argonaut constantly maintains the same re- 

 lative position in its shell. 



" 2nd. The young cephalopod manifests the same concordance between 

 the form 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. 



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

 fundus of the sac begins to be withdrawn from the apex of the shell only 

 when the ovarium begins to enlarge under the sexual stimulus. 



" 4th. The shell of the argonaut corresponds in size with that of its in- 

 habitant, whatever be the differences in the .latter in that respect. (' The 

 observations of Poli, of Prevost, and myself, on a series of Argonauta rufa 

 before cited, are to the same effect.') 



" 5th. The shell of the argonaut possesses all the requisite flexibility and 

 elasticity which the mechanism of respiration and locomotion in the inha- 

 bitant requires ; it is also permeable to light. 



" 6th. The cephalopod inhabiting the argonaut repairs the fractures of its 

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

 shell, and differing in mechanical properties only in being a little more opake. 



u 7th. The repairing material is laid on from without the shell, as it 

 should be according to the theory of the function of the membranous arms 

 as calcifying organs. 



" 8th. When the embryo of the argonaut has reached an advanced stage 

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

 loped. 



" 9th. The shell of the argonaut does not present any distinctly defined 

 nucleus. 



" Mr. Owen finally proceeded to consider the validity of the best and 

 latest arguments advanced in favour of the parasitism of the cephalopod 

 of the argonaut, and commenced with those published in the Proceedings 

 of the Zool. Society for 1836, p. 122. 



"Mr. Gray states, 1st. 'The animal has none of those peculiarities of 

 organization for the deposition, formation, and growth of the shell, nor 

 even the muscles for attaching it to the shell, which are found in all other 

 shell-bearing molluscs ; instead of which, it agrees in form, colour, and 

 structure with the naked molluscs, especially the naked cephalopods.' 



" To this statement it need only be replied, that the cephalopod of the 

 argonaut possesses two membranous expansions, having the same structure 

 as the calcifying processes of the mantle in the testaceous molluscs, and 



