373 



a firm bond of union to the horny girdle of the mantle, and by- 

 means of this to the sides of the last chamber of the shell — in 

 the higher Cephalopods these muscles are always in relation to 

 the development of the internal shell or framework ; in Octopus, 

 Loligo, and Sepia, these muscles arise from the base of the arms 

 and the cephalic cartilage, and are attached to the sides of the 

 mantle and to the capsule of the calcareous plate — in Argonaut, 

 which has no internal shell, these muscles are smaller even than 

 in the naked Octopus, and reduced to a few fibres lost in the 

 mantle ; there is no muscular connection between the body and 

 the external shell. This has been alluded to by Owen,* as 

 affording a strong analogical argument in favor of the opinion 

 that the Argonaut shell does not form an integrant part of the 

 animal which inhabits and deposits its eggs in it ; as it seems 

 hardly probable, says he, considering the intimate relation be- 

 tween the shell and the means of attachment in other Cephalo- 

 pods, that this animal, with a highly developed external shell, 

 should have its attachment reduced to a lower degree than in the 

 naked Octopus. t The Serpula, however, an Annelid, can secrete 

 as true a shell as the Argonaut, and has as little muscular con- 

 nection with it ; it can also take different positions in its shell, 

 quit it and return to it. as is doubtless true of the Argonaut — so 

 that these facts do not prove any thing in favor of the parasitism 

 of the Argonaut. 



The funnel is entire, and without a valve, articulated to the 

 inner sides of the mantle by a cartilaginous ball-and-socket joint. 

 The eyes are large and sessile ; the organ of hearing is well 

 developed in the substance of the cephahc cartilage. 



The jaws consist of two horny mandibles, moving vertically, 

 like a parrot's beak. The oral cavity has a well developed 

 tongue, partly papillose, and partly spiny, the points directed 



* Memoir on the Pearly Nautilus, p. 19, London, 1832. 



t [In a recent letter to the author, Isaac Lea, Esq., of Philadelphia, says, in 

 relation to the A. argo : " There is a muscular attachment, and, small as it may 

 be, it is not at all anomalous. In all the spiral shells, the attachment is small, 

 and it is transfen-ed in its position as the individual increases in size, enlarging 

 its ' house.' M. Blauchard procured and examined six living specimens, and 

 ascertained that the hard and soft parts were attached by a ligament." (Ann. 

 Lin. Soc. de Bordeaux, Vol. 3.)] This is opposed to the opinions of the best 

 ■writers on the subject, both English and continental. 



