1073 



NAUTILID,. 



NAUTILID.&. 



1074 



Series,' No. 499, A.) is a preparation exhibiting the crop, gizzard, and 

 laminated pancreatic pouch. (See the ' Catalogue,' vol. i.) 



Circulating and Respiratory System. The respiratory organs are 

 longated and pyramidal, and have the same laminated structure and 

 symmetrical disposition as in the Cuttle-Fish; but they are four in 

 number, being disposed two on either side, and each pair arising by 

 a common peduncle from the inner surface of the mantle. " From 

 this difference in the number of branchiae, in addition to the other 

 peculiarities in the structure of Nautilus," says Professor Owen, " the 

 existence of at least two orders of the class Cephalopoda, is, I imagine, 

 demonstrated ; and the denominations of these orders might con- 

 veniently be taken from the modifications of the respiratory system. 

 Assuming therefore that it is common to the class to possess brauchiso 

 of a laminated structure, symmetrically disposed, and concealed 

 beneath the mantle, those genera which possess two such branchiae 

 will form an order under the term Dibranchiata, and the Pearly 

 Nautilus and other Celphalopods with shells of an analogous forma- 

 tion, a second order, under the term Tetra6ranchiata. It is in this 

 sense that the expression ' Dibranchiate Cephalopods' has been made 

 use of in this memoir; and to this group most of the characters of 

 the class, as given by the immortal Cuvier in his ' Regne Animal," 

 exclusively appertain." [CEPHALOPODA.] 



Nervous System and Organs of Sense. This part of the system in 

 the iarly Nautilus is in many respects inferior to that of the 

 Dibranchiate Cephalopoda, though it is analogous to it. " The part," 

 says Professor Owen, " which corresponds to the brain of the cuttle- 

 fish, neither enlarged nor lobulated, nor contained in a carti- 

 laginous receptacle; but is a simple rounded chord or commissure 

 placed transversely above the oesophagus, and connected at its 

 extremities to the great ganglions. These are six in number; are 

 disposed symmetrically about the oesophagus, and, together with the 

 central commissure, are loosely enveloped in a tough membrane, or 

 dura mater." The double oesophageal collar is not peculiar to 

 Nautilus, but is also found in other Molluscs, Aplysia for example ; 

 though in these latter cases the subccsophageal ganglions being more 

 remote, the connecting filaments running to the common centre above 

 are longer. In the Museum of the College of Surgeons a preparation 

 (No. 1306, A, 'Physiological Series') exhibits the head and anterior 

 or muscular part of the body of this species laid open longitudinally 

 along the dorsal aspect, and the sides divaricated to show this part of 

 the system. The brain, or supracesophageal mass, will be seen to 

 consist of a transverse chord-like ganglion, from the ends of which 

 three nervous trunks are continued on each side. The anterior pair 

 pass downwards and forwards by the sides of the oesophagus to unite 

 below it, forming a ganglion on either side ; these supply the digital 

 processes and tentacles, and give off nerves to the organ of smell and 

 the funnel. The middle and superior trunks dilate into the optic 

 ganglions ; the retina, which terminates that of the left side, is shown. 

 The posterior chords surround the oesophagus in a manner analogous 

 to the anterior pair, forming also two ganglionic swellings, from which 

 the nerves of the great shell-muscles and those of the viscera are 

 given off; the latter nerves are of small size, and are continued 

 down by the side of the great perforated vein, and are analogous in 

 their distribution to the sympathetic nerves and par vagum. (' Cat.,' 

 vol. ill. part 1.) 



Sight. The eye of the Nautilus, as might be expected from the 

 comparative inferiority of the brain, is less complex than in the 

 Dibranchiate Cephalopods. "Indeed," says Professor Owen, "it 

 appears to be reduced to the simplest condition that the organ of 

 vision can assume without departing altogether from the type which 

 prevails throughout the higher classes. For although the light is 

 admitted by a single orifice into a globular cavity or camera obscura, 

 yet the parts which regulate the admission and modify the direction 

 of the impinging rays are entirely deficient." The eyes are not 

 situated in orbits, but are attached severally by a pedicle to the side 

 of the head, immediately below the posterior lobes of the head. This 

 attachment to a muscular pedicle gives great mobility to the organ, 

 and enables the animal easily to bring it to bear on objects in a 

 variety of directions. Professor Owen found that the contents of the 

 globe had escaped by the pupil ; but he comes to the conclusion, on 

 satisfactory grounds, that if it had ever contained a crystalline lens, 

 it must have been very small. 



Professor Owen was unable to detect a distinct organ of hearing. 



The structure of the tongue and the nerves with which it is supplied 

 indicate a considerable development of the faculty of taste; and the 

 numerous tentacles, soft in their texture, annulated on their surface, 

 and well supplied with nerves, must give the animal an ample enjoy- 

 ment of the sense of touch. 



Generative System. Aristotle was well aware of the distinctions of 

 sex in the Ma\dnia ; and Professor Owen remarks that the propriety 

 with which that great zoologist classed this animal, although it was 

 covered with a shell to which it adhered like a snail, is fully borne out 

 by the dissection of the female, upon which he operated. The organs 

 consist of an ovary, an oviduct, and, as in the Pectinibranchiate Gas- 

 teropoda, of an accessory glandular apparatus, and are delineated in 

 the eighth plate of Professor Owen's ' Memoir.' 



With regard to the habits of the Nautilus, Rumphius says, " When 

 he floats on the water he puts out his head and all his barbs (tentacles), 



NAT. HIST. DIV. VOL. III. 



and spreads them upon the water, with the poop (of the shell) above 

 water : but at the bottom ho creeps in the reverse position, with his 

 boat above him, and with his head and barbs upon the ground, 

 making a tolerably quick progress. He keeps himself chiefly upon the 

 ground, creeping sometimes also into the nets of the fishermen; but 

 after a storm, as the weather becomes calm, they are seen in troops 

 floating on the water, being driven up by the agitation of the waves : 

 whence oue may infer that they congregate in troops at the bottom. 

 The sailing however is not of loug continuance ; for having taken in 

 all their tentacles, they upset their boat, and so return to the bottom," 

 (' Rariteit-Kamer.') 



Professor Owen, who quotes this passsage, observes that the extent 

 to which the Pearly Nautilus is covered by its shell, and its close 

 attachment to it, indicated the affinity to the Gasteropoda in too 

 strong a manner to escape the penetration of Aristotle, who, as we 

 have seen, directly compares it in this respect to" a snail ; " and the 

 general resemblance," says Professor Owen in continuation, " must 

 have been sufficiently striking, when, with his house above him and in 

 the supine position, he makes his way along the sand with a moderate 

 degree of rapidity." 



We here give representations of the external appearance of the 

 shells of two species. 



Shell of Nautilus rompiUtu. 



Shell of Umbilicatccl Nautilus (yautilui serobiculatut). 



The genus Nautilus is thus characterised by Professor Owen. Body 

 oblong, rounded posteriorly, terminated by a slender membranaceous 

 tube. Head above with an ambulatory disc. Arms on each side, 1 9. 

 Tentaculiferous labial appendages 4, disposed around the mouth. 

 Tentacles (92 !) of three kinds, namely : ophthalmic, lamellose, on 

 each side two ; brachial, annulose, on each side 20 ; labial, annulose, 

 on each side 24. The whole body laid up in the last chamber of a 

 large multilocular shell, and affixed by two lateral muscles. [TBTBA- 



BKANCHIATA.] 



The species inhabit the seas of warm climates, especially those of 

 Asia and Africa, and their islands, Amboyna, Zanzibar, and New 

 Guinea; aud the Pacific and Australian Oceans. 



3 z 



