45 



valid as evidence of the parasitism of the Cephalopod ; and it is now 

 proved that the transparent film observed by M. Rang to be de- 

 posited by the Ocythoe over the fracture of the Argonaut shell 

 would have been converted into a true shelly material if the sub- 

 ject of his experiment had survived for a longer period. 



" M. d'Orbigny *, on the other hand, derived from his observations 

 of the Argonauta Mans made during his voyage to South America, 

 a belief in the fallacy of the parasitic theory ; the principal argu- 

 ment of novelty vi^hich he adduces is founded on the integrity of the 

 delicate and flexible margins of the shell in which the supposed pa- 

 rasite was lodged. M. de Blainville has refused his assent to the 

 validity of this argument on the grounds that the rightful owner of 

 the Argonaut shell might have been very recently expelled from 

 the specimens described by M. d'Orbigny. As I have elsewhere f 

 considered this objection, I shall not dwell further upon it, but 

 merely observe that the experiments of Poli and Ranzani adduced 

 by M. d'Orbigny in evidence of the formation of the shell in ovo 

 are more than suspicious, and are inadequate to enforce a conviction 

 of the trtith of the non-parasitic theory. 



" The more recent arguments of M. de Blainville J in favour of the 

 parasitism of the Argonaut repose partly on statements which are not 

 based on facts, and partly on the interpretation of actual facts. The 

 false facts are the following: 1st. That the same species of Cepha- 

 lopod is not always found in the same species of shell. 2nd. That 

 the natural position of the animal in the shell varies, the back of the 

 animal being sometimes next the outer wall of the shell, sometimes 

 next the involuted spire. 3rd. Tliat the animal does not occupy the 

 posterior part of its shell — (this being true of the more mature ani- 

 mal only). 4th. That the form of the animfd and of its parts offers no 

 concordance or analogy with the shell. 5th. That the shell is too 

 opake to have permitted the influence of light in the development of 

 the coloured pigment in the mantle of the Cephalopod of the ArgOr 

 naut. 6th. That it is very far from being true that the Argonaut 

 shell possesses the flexibility and elasticity requisite to harmonize 

 with the locomotive and respiratory movements of the animal. 7th. 

 That the animal suffers no appearance of inconvenience when de- 

 prived of its shell. 8th. That a Cephalopod has been discovered in 

 the Sicilian seas like that which inhabits the Argonaut, but without 

 a shell. 



"With respect to the first six of these statements, it need only to be 

 observed that they are abundantly disproved by the series of speci- 

 mens now on the table. .. 



"As to the seventh statement, its value vrill be manifest, when the 

 account given by Mr. Cranch, on which it is founded, is carefully 

 analysed and considered. Mr. Cranch's observations, as quoted by 

 Dr. Leech, amount simply to this : ' When the Cephalopod (Argo- 



• Voyage dans I'Amirique Meridionale, MoUusques, p. 10. 



t Zool. Trans., vol. ii. p. 114. 



X Annates d'Anatomie et de Physiologie, Mai, 1837. 



