Elements of comparative anatomy, tr. by F.J. Bell. The tr. revised and a preface written by E.R. Lankester - Softcover
Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1878 Excerpt: ...by a fold of the mantle, occupies the hinder part of the hack, and so forms that region which is ordinarily known as the ventral surface. To make these relations clear we must imagine the animal placed in such a position that the aboral end points upwards, and the head forwards and downwards (cf. Fig. 172). All the body above the head would then correspond to the dorsum of the Gastropoda. The mantle is sometimes separated from the head by a circular groove (Sepia); sometimes this fold of the mantle is directly continuous with the integument of the head at the sides of the neck (Octopus), so that the mantle forms a fold above the branchial cavity only. Lateral processes of this mantle function as locomotor organs (fins); in the Sepiadaa they are generally small, and extended along its whole length; in the Loliginidas they are broader, but are limited to the aboral end of the body. The formation of the mantle-cavity and the position of the anus lead us to the conclusion that this arrangement is due to the primitive possession of a shell which covered the whole mantle; and, indeed, the shelled Cephalopoda are by far the older forms, while the remarkable variations seen in the characters of their shells lead us to think that this structure had a very ancient origin. An organ which has the same position as the foot of the Gymnosomatous Pteropoda--the funnel--corresponds to the foot of the Gastropoda. In Nautilus it is formed of two lamellae, which arise from the ventral surface below the head, and which form a tube by being rolled over one another; this tube projects from the mantle-cavity (Fig. 175, i). In the Dibranchiata this organ cannot be seen to be composed of two lateral parts, except in the embryo; they take their origin in the space between tho mantle ...
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