. L'anatomie comparée et de la physiologie. . Chap, x.j MOUVEMENTS D'ACCORD À A. 381 considérablement augmentée, et forme des epipodia, et ces, soit indépendamment ou en conjonction avec la partie médiane du pied, se convertir en puissants ailerons musculaires. Dans le le epipodia Cephalopoda forment un entonnoir, par laquelle l'eau de la respiration est expulsé à l'extérieur ; cette expulsion de l'eau vers l'avant entraîne un mouvement en arrière de l'animal. Dans le Tetrabraiichiata (Nautilus) les bords de l'epipodia ne sont pas, comme dans e Dibranchiata, fusionnées avec l'autre, mais simplement pliée sur. Parmi

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. Comparative anatomy and physiology. . chap, x.j MOVEMENTS OF CHORD AT A. 381 greatly enlarged, and form distinct epipodia, and these, either independently or in conjunction with the median part of the foot, become converted into powerful muscular fins. In the Cephalopoda the epipodia form a funnel, through which the water of respiration is expelled to the exterior; this expulsion of the water forwards results in a backward movement of the animal. In the Tetrabraiichiata (Nautilus) the edges of the epipodia are not, as in th Dibranchiata, fused with one another, but merely folded over. Among the Chor- «lal:i locomotion is effected by swimming, Fis- lei.-Carinorio eymbium. i n rn r» i r» o- r>vppniTi cr m' Proboscis ; t, tentacles ; / foot; d, disc ; J Um ping, epillg, St shell; g, branchiae. walking, or flying, and all these activities are presented by marine as well as by terrestrial forms. Swimming organs have the form of more or less broad plates, which may or may not be supported by bone. The simplest cases are presented by the mere flattening or expansion of an organ ; this, for example, obtains in the tadpole, the newt, or the insectivorous form Potamogale velox, where the tail is flattened from side to side and forms a powerful locomotor organ. In the Cetacea, on the other hand, which require to come repeatedly and rapidly to the surface of the water, the tail is flattened from above down- wards. In more complicated cases, as in many fishes, the tail, which is here also the most important organ of locomotion, and has a screw-like movement, is aided by the caudal fin when that is well developed ; the paired lateral fins are in most cases rather organs of support and direction, than of locomotion ; but in some. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.. Bell, F. J. (Francis Jeffr

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