FUNNEL AND CAPITO- PEDAL CARTILAGE. 765 



may be gathered from such a dissection as that represented in fig. 1, PI. LXXXL, that 

 the main axis of the cephalopodium. as indicated by the general trend of the tentacular 

 sheaths, does not coincide with the skeletal axis but describes an angle with it. I shall 

 refer to this matter again under the heading " Flexure and Orientation," but meanwhile 

 I cannot help thinking that the occurrence of conflicting axes in relation to the 

 cephalopodium of A\iutilus may have morphological significance, as affording evidence 

 of profound topographical changes which have upset the primitive axial simplicity. Such 

 an axial disturbance is no longer apparent in the Dibranchiata, so that whatever it may 

 indicate, it is at all events a remarkable feature in the organisation of Nautilus and 

 should be, though it never has been, taken into account. 



The limit of the extension of the anterior comua into the crura of the funnel is 

 superficially indicated on each side by the presence of a limbate border (l). These comua 

 do not reach to the base of the tongue-like valve which is inserted upon the inner 

 surface of the dorsal wall of the funnel. 



The posterior comua underlie the optic ganglia, the olfactory labjTinths (rhinophores) 

 and the otocysts in the order named (cf PI. LXXXI. fig. 5), but do not embrace these 

 structures. Into the hinder extremities of the posterior comua are inserted the retractor 

 muscles of the buccal cone (PI. LXXXI. fig. 7), and the angles in which the insertion 

 takes place constitute deep pits in the fundus of the peristomial haemocoel. 



The funnel itself comprises several regions which differ in colour, texture and function. 

 Its anterior and posterior portions are separated from one another by the anterior cornua 

 and body of the cartilage. At the forward limit of the latter there occurs externally 

 a peculiar border or liinbus, the linibus in/undibuli (1). If the funnel be cut across behind 

 the livibus the whitish crura in/undibuli penetrated by a pair of subcylindrical muscles, 

 the levatores in/undibuli of Owen, lying in their own venous sinus on each side, are 

 seen to be clearly separated by the anterior cornua of the cartilage, from the soft brownish 

 yellow alae in/undibuli which extend backwards and dorsally to the base of the nuchal 

 membrane. (PI. LXXXII. fig. 3.) It is one of the best kno\vn peculiarities of the 

 organisation of Nautilus that the funnel is cleft down the ventral surface, so that its 

 flaps overlap and present a free border throughout their entire length. The anterior 

 portion of the free borders of the flaps belongs to the region of the cruia, and the 

 posterior portion to that of the alae, although of course quite continuous. The crura 

 are united together dorsally by the thin median wall of the funnel which rests in the 

 infimdibular fossa of the great oral sheath and carries, on its inner surface, the large 

 valve of the funnel. Behind this thin-walled anterior portion, the dorsal wall of the 

 funnel, between the alae, is greatly thickened owing to the presence of the spongy 

 compressor muscle, the transverse fibres of which are inserted into the median keel of the 

 cartilage {carina cartilaginis). 



In the fresh condition the integument which covers the compressor muscles and the 

 adjoining surface of the ala£ in/undibidi is found to be a slimy, mucous membrane, forming 

 two large pads meeting in the middle line and constituting the mucus-gland of the funnel. 

 It is interesting to note that Jatta' has interpreted the funnel-organ of Dibranchiate 



' .latta, G., "Sopra I'organo dell' imbtito nei Cefalopodi." Boll. Soc. Xtrpoli (Ser. 1) vii. 189.S, pp. 4.5—60, 

 Tav. IV. The funnel-organ is eometimes called the "Organ of Verrill" or "Organ of Miiller." Cf. Hojle, W. E., 

 " ObBervations on the anatomy of a rare Cephalopod (Gonatus fabricii)." P. Zool. Soc. London, 1889, p. 128. 



100—2 



