PROF. OWEN ON THE ARGONAUT. 429 



sufficiency depends upon the circumstance that in forming them the condi- 

 tion of the mature argonaut has heen considered as applicahle to every 

 period of its life, and the arguments Nos. 1 and 2 being founded upon 

 that supposition, thereby fall to the ground. In the argument for the pa- 

 rasitic theory deduced from the development of the argonaut-shell, a gene- 

 ral rule, applicable to an extensive primary division of the animal kingdom, 

 is assumed from the result of extremely scanty observations, which are al- 

 together inadequate to its establishment. 



"'In the Proceedings of the Zoological Society for 1837, Mr. Charles- 

 worth proposed an argument in favour of the parasitism of the Ocythoe, 

 which has the merit — not possessed by those above discussed — of being 

 founded on the observation of a new fact in the natural history of the ar- 

 gonaut, viz. that breaches in the shell were repaired by a substance agree- 

 ing in every respect with the original shell. Mr. Charlesworth has, however, 

 since admitted that this fact is not valid as evidence of the parasitism of 

 the cephalopod ; and it is now proved that the transparent film observed by 

 M. Rang to be deposited by the Ocythoe over the fracture of the argonaut- 

 shell, would have been converted into a true shelly material if the subject 

 of his experiment had survived for a longer period. 



" * M. d'Orbigny, 1 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 argument of novelty which he 

 adduces is founded on the integrity of the delicate and flexible margins of 

 the shell in which the supposed parasite 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 2 con- 

 sidered this objection I shall not dwell further upon it, but merely observe 

 that the experiments of Poli and Ranzani, deduced 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 truth of the non-parasitic theory. 



" ' The more recent arguments of M. de Blainville 3 in favour of the pa- 

 rasitism 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 cephalopod 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. That the ani- 

 mal does not occupy the posterior part of the shell— (this being true of the 

 more mature animal only). 4th. That the form of the animal 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 argonaut. — 

 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 ap- 

 pearance of inconvenience when deprived of its shell. 8th. That a cepha- 

 lopod 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 ob- 

 served that they are abundantly disproved by the series of specimens now 

 on the table. 



1 Voyage dans l'Amerique Meridionale, Mollusques, p. 10. 

 2 Zool. Trans", vol. ii. p. 114. 3 Ann. d'Anat. et de Physiol. Mai, 1837. 

 Vol. III.— No. 33. n. s. 2 z 



