of Nautilus Pompilius. 59 



with the organization, and in particular with the organs of pro- 

 pagation of these animals. Less notice has been taken of the 

 external sexual difference ; but from the silence of writers it 

 might be suspected that the difference in question must be on 

 the whole not great or interesting, as indeed in some species 

 we know with certainty that such is the case*. To this, how- 

 ever, besides the genus Argonauta, some species also of the 

 genus Octopus form exceptions. In male individuals of the last- 

 named animal one of the arms lies in a bladder, from which it is 

 developed at the time of copulation, is detached from the body 

 and is taken into the shell of the female, where some years 

 ago it was several times met with, and fii'st, under the name of 

 Hectocoti/lus-f and Trichocephalus acetabularisX,was regarded as 

 a parasitic animal form, and afterwards as the male animal itself, 

 before the true bearing of the matter, as we have given it in few 

 words, was recognized §. 



Ever since the animal that inhabits the shell so long known 

 as Nautilus Pompilius was described by Owen||, the principal 

 question remained here also for investigation — what is the amount 

 of sexual difference in this species ? The individual so admirably 

 investigated by Owen was a female, as were also those which 

 were described after him by Valenciennes and W. Vrolik^. The 

 question, bow far the general structui-e as well as the external 



* In Loligo the female appears to be more elongate, at least Verany 

 states this to be the case in Loligo vulgaris and Loligo sagittata. (Mol- 

 lusques mecUterraneens. Genes, 1851, 4to, pp. 99, 109.) In Sepia officinalis, 

 on the other hand, the female is rounder, and the males differ in having a 

 white stripe around the fins {ibid. p. 69). In Sepiola dispar, Krohn lias 

 observed that the female is distinguished by larger suckers (Verany, ibid. 

 p. 65). Delle Chiaje states that the males remain smaller, and that, par- 

 ticularly in Loligo sagittata, the male is one-fourth shorter than the female. 

 (Memorie sulla Storia e Notomia degh Animali senza Vertebre del Regno 

 di Napoh. 1829, p. 97.) 



t Cuvier in the Annales des Sc. Nat. xviii. 1829, pp. 147-156. 



X Delle Chiaje, Memorie sulla Storia, &c., ii. 1825, p. 225. 



§ See on this discovery Verany, op. cit. pp. 126-12.9, pi. 41 ; H. Miiller, 

 Ueber das Mannohen von Argonauta Argo und iiber die Hectocotylen ; 

 Zeitschrift fiir vvissensch. Zoologie, iv. 185c5, s. 1-35. tab. 1 ; compare 

 Verany and Vogt, Ann. des Sc. Nat. 3 se'rie, xvii. 1852, Zool. pp. 147-188, 

 pi. 6-9, and R. Leuckart, Ueber die Hectocotylen von Octopus CarencB; 

 Zool. Untersuchungen, 3tes Heft. (Of this arm there must thus be an 

 annual reproduction, respecting which I do not know whether any actual 

 observations have been obtained.) 



II Memoir on the Pearly Nautilus. London, 1832, 4to. 



IT Valenciennes, Nouvelles recherches sur le Nautile flambe. Archives 

 du Museum, ii. 1841, p. 257-314; W. Vrolik, Brief aan den Gouverneur- 

 Generaal J. J. Rochussen, over het ontleedkundig zamenstel van den Nau- 

 tilus Pompilius, in the Tijdschrift voor de wis- en natuurkundige Weten- 

 schappen, uitgegeven door de Eerste Klasse van het Koninklijk Neder- 

 landsche Instituiit, ii. 1849, bl. 307-324. 



