. Elements of conchology / Prepared for the use of schools and colleges. Mollusks. 20 STRUCTURE OF CEPHALOPODS. viscera and is open only in front, {fig. 8, o). The head issues from this opening: it is round and generally provided with two round eyes, very analogous in their structure to those of verte- brate animals. The mouth occupies the centre : it is armed with two jaws; and around this opening is found a crown of flexible and fleshy appendages, which are termed, indifferently, legs or arms, because they seem to be entitled to either appella- tion ; for they serve both as organs of prehens
. Elements of conchology / Prepared for the use of schools and colleges. Mollusks. 20 STRUCTURE OF CEPHALOPODS. viscera and is open only in front, {fig. 8, o). The head issues from this opening: it is round and generally provided with two round eyes, very analogous in their structure to those of verte- brate animals. The mouth occupies the centre : it is armed with two jaws; and around this opening is found a crown of flexible and fleshy appendages, which are termed, indifferently, legs or arms, because they seem to be entitled to either appella- tion ; for they serve both as organs of prehension and locomo- tion {fig. 7). 8. The cephalopods are essentially aquatic animals, and consequently they breathe by means of branchias. These organs are always perfectly symmetrical, and are found con- cealed beneath the mantle, in a particu- lar cavity {fig. 8), the parietes of which alter- nately contract and di- late, and the ulterior communicates exter- nally by two openings; one (o) in form of a slit, serving for the entrance of the water, and the other pro- longed in the shape of a tube or funnel (^), serving for the escape of water and excre- ment. Each branchia (/;), which is in form of an elongated pyra- mid, the summit of which is directed forward, is composed of a great number of membranous lamellse or leaves, placed transversely and fixed on each side of a middle stalk. Each one of these leaves divided into lamellas, which are in turn it is in their substance that we find the. Fig. 8. BODY OF A POULPE. IS again subdivided, and capillary vessels where Explanation of Fig. 8.—The body of a poulpe seen from beneath (the mantle is slit up on tlie middle line, and, on one side, raised up to show the interior of the respiratory cavity):—a. the base of the head ;—t. the tube by which tlie water escapes from the respiratory cavity ;—o. one of the two lateral openings through which the water enters tiiis cavity ;—b. one of the branchiae or gills. 3. Hov/ do cephalop
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectmollusks, bookyear184
