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Show 680 MR. J. GRAHAM KERR ON THE [June 18, projects parallel to the axis of the buccal mass-quite free and separated by a deep groove from the hood and tentacle-mass. Tongue-like in form, its margins are inrolled about a longitudinal axis, so that one comes to overlap the other. Which does so appears to be quite inconstant in different individuals, and in any one individual the right and left margins present exactly the same appearance ; there being nothing to point to one in particular being kept habitually folded over the other. From this, and from the general muscular character of the funnel, I have little doubt that the living animal possesses the power of unrolling and flattening it out, possibly even of using its broad lower face to creep on or adhere to rocks. In spirit-specimens one can readily so unroll the funnel, and when this is done the appearance of the animal is very striking, as is shown in PI. X X X V I I I . fig. 1, where, by the way, the mantle-flap has been partially removed so as to afford a better view of the creature. One is here impressed, first of all, by the sharp way in which the funnel is marked off from the hood-tentacle- head mass. Everywhere a deep groove separates them l. There is nothing here to suggest or even support the view that part of the foot has grown up round and become fused with the head. Again, the great size of the organ is very impressive-more especially its width from side to side,-and its entire condition is such as at once, to m y mind irresistibly, to suggest that in this organ one has the representative of the whole of the foot of the ordinary Gasteropod. The general relations of the parts in Nautilus impress upon one that :- (1) The hood-tentacle complex is preponderatingly anterior (dorsal) to the buccal mass, its posterior (ventral) parts being relatively insignificant. (2) The hood-tentacle complex is most sharply marked off from the funnel by a deep groove. (3) The funnel is enough, in itself, to represent the whole of the Gasteropod foot. Considering merely them alone, there is no suggestion of doubt that the hood-tentacle complex is cephalic ; that the funnel is the Gasteropod foot. It is because, at the present time, after many years of controversy, the contrary view, which for shortness may be referred to as the ' pedal' view, has gained the ascendency and has come to be the one enunciated by the most authoritative text-books2, that the present discussion seems necessary. W h e n Lankester published his 'Encyclopaedia Britannica' article on Mollusca, he pointed out that the view taught bv Leuckart, Loven, Huxley, and himself, that the Cephalopod arm's 1 In this connection the figure given by Lankester (Zoological Articles, fig. 91) though very corroborative of the view there advocated, seems scarcely in accord with the actual conditions. 2 Lang's Lehrbuch, pp. 587, and Korschelt and Feider, p. 1176, |
