Dr. G. Bennett on the Pearly Nautilus. 333 



water from a tube (the funnel?), after the manner of the 

 cuttlefish and other Cephalopods. However, leaving the 

 depth to which it can descend a matter for further inquiry, a 

 question arises, By what power is the animal enabled to regu- 

 late its movements of ascent and descent in the water? The 

 use of the chambers in the shell is still a matter of specula- 

 tion ; they are most probably air-chambers destined to assist 

 the specific gravity of the animal ; and possibly they may 

 generate nitrogen gas. Professor Owen says, " In acquiring 

 the camerated structure of the shell the Nautilus gains the 

 power of rising from the bottom, and the requisite condition 

 for swimming, by the exhalation of some light gas into the 

 deserted chambers it attaches to its otherwise too heavy body, 

 a conti'ivance for ascending in its atmosphere, as we ascend 

 into ours by the aid of a balloon. But the Nautilus, superior 

 to the human aeronaut, combines with the power of elevating 

 and suspending itself in the aqueous medium, that of opposing 

 its currents and propelling itself at will in any direction. It 

 possesses the latter essential adjunct to the utility of the bal- 

 loon as a locomotive organ, by virtue of the muscular funnel, 

 through which it ejects into the surrounding water, doubtless 

 with considerable force, the respiratory currents." He also 

 says, '' It appears that the proportion of the air-chambers to 

 the dwelling-chamber of the Nautilus and its contents is such 

 as to render it of nearly the same specific gravity as the sur- 

 rounding water. The siphon which traverses the air-chambers 

 communicates with the pericardium, and is most probably filled 

 with fluid from the aquiferous cavity." To whatever depth 

 these animals are capable of descending, and whatever may be 

 the amount of pressure they can endure, they no doubt can 

 readily ascend to the surface of the ocean by the means explained 

 by Prof. Owen; and we well know they can float upon die water, 

 as proved by the specimen I captured at Erromanga, and can 

 crawl upon the reefs, as verified by the natives, who thus 

 catch them in their baskets (drawings of which and mode of 

 capture are given in my ' Gatherings of a Naturalist ') . 'J^hey 

 are also now well known to be thrown on shore during heavy 

 gales, and are then sought for and secured as an article of 

 food by the natives, who consider them good eating. They 

 have also been found thrown upon tiie coral reefs, as in an 

 instance mentioned by my friend Dr. M'Donald, R.N., who, in 

 his paper on the Anatomy of Nautilus umhilicatus (rightly 

 macromphalus^ because umbilicatus is not found at the Isle of 

 Pines?), says, " H.M. steamvessel ' Torch,' having visited 

 the Isle of Pines in the month of July 1854, one of the officers 

 had the good fortune to pick up a recent specimen of Nautilus 



