116 MR. OWEN'S DESCRIPTIONS OF 



from its oviducts, and attached to tlie shell. When first captured, the ova were pressed 

 down into the back part of the shell ; but upon the removal of the superincumbent 

 weight of the animal, it would appear that their own elasticity, combined perhaps with 

 the absorption of fluid, and the coagulation of the albumen by the alcohol, had tended 

 to occasion their protrusion forwards. 



The longest diameter of the shell is nine lines ; the transverse diameter six lines : the 

 length of the animal, from the fundus of the sac to the end of the longest arm (the se- 

 cond), one inch four lines ; the length of the sac, from its fundus to the free margin at the 

 base of the funnel, five lines. The funnel extends beyond the base or uniting membrane 

 of the ventral pair of arms ; it is, as in the other genera of Octocera, unprovided with 

 an internal valve ; but is articulated at its base by two lateral joints to the mantle. 

 The account of this structure in the Philosophical Transactions does not convey an 

 adequate or correct idea of what the present specimen of Ocythoe Cranchii presents ; 

 there appears indeed to be a typographical error in Dr. Leach's description. I find on 

 each side of the base of the funnel, immediately above the insertion of the lateral mus- 

 cular pillars, a small firm fleshy tubercle, above which there is a small depression ; on the 

 inside of the mantle immediately opposite, there is a corresponding tubercle and cavity, 

 but their positions are reversed, the tubercle being above the cavity; thus the promi- 

 nences in the funnel and mantle are reciprocally received into the opposite depres- 

 sions, and the funnel and mantle are locked together by a double ball and socket joint, 

 in the degree of apposition necessary for the complete fulfilment of the vigorous alter- 

 nating muscular actions on which the respiratory function depends (a, b, fig. 14. PL XXI.) 



The arms in Mr. Bennett's Argonauta Mans were not rigidly contracted, as happens 

 generally with those specimens which are immersed aUve in spirits ; but were flaccid and 

 flexible, and well adapted for determining their exact proportions and form. The length 

 of the first pair was nine lines ; the number of suckers on each of these was thirty-six j 

 they extend, as in Argonauta Argo, along the circumference of the terminal membrane, 

 but not to the same distance. I could not trace them with the microscope further than 

 about one third of the way down from the anterior margin of the membrane ; while in 

 Arg. tuherculata they may be traced along more than half the circumference of the velum ; 



pulie, e. g., instances of soft-bodied invertebrates secreting as true a shell as the calcareous Argonaut, yet having 

 as little of a muscular attachment or uniform position to the shell, and as much freedom of quitting their shell 

 and returning to it, as the Argonaut. 



With respect to another argument*, in favour of the parasitism of the Cephalopod of the Argonaut, which, 

 from an imperfect knowledge of the circumstances attending the development of the ova of the MoUusca, was 

 supposed to be afforded by a difference in the size of the ova of the Ocythoe, and of that which Mr. Gray regards 

 as the' nucleus of the Argonaut shell ; I refer to it only because it has been adopted by M. De Blainville in 

 his resume of the Argonaut question as valid in favour of the parasitism of the Ocythoe : it has, however, since 

 been abandoned by its promulgator, being founded on erroneous premises. (See the Magazine of Natural 

 History, 1837, New Series, p. 247.) 



* See Proceedings of the Zoological Society for September, 1S34. 



