444 Zoological Society. 



With reference to the second suite of specimens, viz. the ova of 

 the Argonaut in different stages of development, Mr. Owen entered 

 into a detailed account of the new and interesting facts which they 

 revealed. In the ova most advanced, the distinction of head and 

 body was established ; the pigment of the eyes, the ink in the ink- 

 bladder, the pigmental spots on the skin, were distinctly developed ; 

 the siphon, the beak, — which was colourless and almost transparent, 

 — and the arms were also discernible by a low microscopic power ; 

 the arms were short and simple ; the secreting membranes of the 

 shell were not developed, and of the shell itself there was no trace. 

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

 dependently of any preconceived theory or statement, could be de- 

 duced from the admirable collection of Argonauta Argo due to the 

 labours of the accomplished lady who had contributed so materially 

 to the elucidation of a problem which had divided the zoological 

 world from the time of Aristotle. 



1st. The Cephalopod of the Argonaut constantly maintains the 

 same relative 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 per- 

 fect adaptation of the one to the other, as do the young of other 

 testaceous Mollusks. 



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 the fundus of the sac begins to be withdrawn from the apex of the 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

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

 (** The observations of Poli, of Prevost, and myself, on a series of 

 Argonauta rvfa, before cited, are to the same effect.") 



5th. The shell of the Argonaut possesses all the requisite flexibi- 

 lity and elasticity which the mechanism of respiration and locomo- 

 tion in the inhabitant requires : it is also permeable to light. 



6th. The Cephalopod inhabiting the Argonaut repairs the frac- 

 tures of its shell with a material having the same chemical compo- 

 sition as the original shell, and differing in mechanical properties 

 only in being a little more opake. 



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

 it should be according to the theory of the function of the mem- 

 branous arms as calcifying organs. 



8th. When the embrj'^o of the Argonaut has reached an advanced 

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

 are developed. 



