. Elements of zoölogy. Zoology. SQUIDS, ETC. 71 as the animal grows, the last one occupied always being walled up or divided off by a partition called a septa. The center of all the divisions is penetrated by a tube ; so, though living in the last chamber, the ani- mal is still connected with the first by a long, delicate, fleshy pedicle that extends through it. The different air-cham- bers are filled with gas, and by them the spe- cific gravity of the ani- mal may be increased or diminished. Beneath the mouth is a siphon through which water is ejected, thus forcing them along. On the bottom t
. Elements of zoölogy. Zoology. SQUIDS, ETC. 71 as the animal grows, the last one occupied always being walled up or divided off by a partition called a septa. The center of all the divisions is penetrated by a tube ; so, though living in the last chamber, the ani- mal is still connected with the first by a long, delicate, fleshy pedicle that extends through it. The different air-cham- bers are filled with gas, and by them the spe- cific gravity of the ani- mal may be increased or diminished. Beneath the mouth is a siphon through which water is ejected, thus forcing them along. On the bottom they crawl with the shell upward. They have no ink-bag, and in the female the tentacles or arms number ninety-four. The great fossil Ammonites, three feet across, are extinct relatives of the nautilus. Value.—Shell in ornamental work. Note.—The eye of the nautilus is remarkable in having no diop- tric apparatus, being merely an elevation bearing a minute hole that leads into the globe of the eye, which during life is filled with sea- water, and thus, according to Hensen, in place of a refracting lense and cornea, there is an arrangement for forming an image on the prin- ciple of the pin-hole camera. Order II. Two-gilled Cephalopods {Dibranchiatd); Spirilla {Spirididce).—These small Cephalopods resemble squids, but contain within their bodies a delicate cham- bered pearly shell with separate whorls, the various rooms. Fig. 75.—Section of Nfiutilus pompiliits, showing the chambers and connecting tube containing the fleshy 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 Holder, Charles Frederick, 1851-1915; Holder, Joseph Bassett, 1824-1888, joint author. New York : D. Appleton and company
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1884
