1895.] ANATOJIY OP XAUTILUS POMPILIUS. 679 



To enter in detail into tbe differences as to minor points in the 

 tenets of the yarious upholders of these two views seems un- 

 necessary, as this has already been done by others ^ ; and further, 

 because it is proposed to consider the problem here in its most 

 general aspect — as to whether the Cephalopod arms are cephalic 

 or pedal. 



It may be advisable, in the first place, to inquire whether there 

 is anything in the general relations of the parts to support or even 

 to suggest the second of these views. In ordinary Cuttlefishes it 

 is pretty obvious that there is nothing of the kind — the arms form 

 a continuous circle round the buccal mass — one would naturally 

 suppose they belong to the head. It is therefore important 

 to glance at Nautilus, where, as Lankester has well accentuated, 

 " any divergence from the condition obtaining in other forms has 

 possibly, and even probably, a special significance," and " is not 

 readily to be dismissed as an ' adaptation ' peculiar to that form." '" 



In Nautilus the arrangement of the circumoral lobes and ten- 

 tacles has been described by Bourne and by Lankester, so that it 

 is unnecessary to go into details. Anteriorly (dorsally) is the 

 large fibrous mass of tissue which forms the hood. Laterally, on 

 each side, is an aggregation of tentacles. Anteriorly (dorsally) 

 the mass of tentacle-sheaths is directly continuous with the hood. 

 On slicing away the substance of the hood carefully, it is seen 

 that the bases of all the outer tentacles are embedded in it. The 

 appearance of tentacle-sheaths is due merely to the more or less 

 distinct marking off by superficial grooves of the parts of the mass 

 sarrounding each tentacle. Hood and tentacle-sheaths together 

 form a perfectly continuous mass lying anterior (dorsal) to the 

 buccal mass and curving backwards (do\\'nwards) on either side of 

 it in saddle-like fashion. In the male this is very obvious, the two 

 limbs of the mass being connected together posteriorly merely by 

 a thin shelf. In the female, however, this bears on its inner side 

 the "inferior inner lobe," which bears on each side a group of 

 tentacles and whose appearance suggests a bilateral origin. The 

 main impression given by the tentacle-hood complex is that of a 

 saddle-shaped structure, situated anterior (dorsal) to the buccal 

 mass — its limbs passing backwards on either side of the latter. 

 The anterior (dorsal) part of the complex here predominates : it is 

 developed less equally all round the buccal mass than in Decapods ; 

 its preponderating part is dorsal. 



The next point of interest in the gross anatomical relations of 

 the parts lies in the funnel Avhich, according to the upholders of 

 the " pedal " view, is primitively continuous with the tentacle-hood 

 mass. 



The Funnel. — This is a large tongue-shaped structure attached to 

 the posterior face of the body — to the roof of the mantle-cavity, 

 into which it imperceptibly passes aborally. At its oral end it 



'^ .Cf. especially Pelseneer's admirable summary, ' Challenger ' Eejjort 

 Pteropoda. 



2 Quart, Jpurn. Mior. Science, vol. xxiii. p. 348. 



