. A manual of zoology. PHYLUM MOLLUSCA 3°3 cate spiral structure, the internal cavity of which is not divided into chambers. It is not secreted by the mantle like the shells of other Mollusca, but by the surfaces of a pair of the arms ending in expanded disc-like extremities, which become applied to its outer surface ; its chief func- tion is to carry the eggs. The argonaut inhabits deep water, 70 to 100 miles off the coast of New England, its shells being in very rare cases found cast ashore on our coast south of Cape Fig. 188. — Shell of Argonauto argo. In addition to the shell there i
. A manual of zoology. PHYLUM MOLLUSCA 3°3 cate spiral structure, the internal cavity of which is not divided into chambers. It is not secreted by the mantle like the shells of other Mollusca, but by the surfaces of a pair of the arms ending in expanded disc-like extremities, which become applied to its outer surface ; its chief func- tion is to carry the eggs. The argonaut inhabits deep water, 70 to 100 miles off the coast of New England, its shells being in very rare cases found cast ashore on our coast south of Cape Fig. 188. — Shell of Argonauto argo. In addition to the shell there is in all the Cephalopoda an internal skeleton of cartilage supporting and protecting the nerve-centres and other parts. The cuttle-fishes and other Dibranchiata when alive will be observed to undergo frequent changes of colour, and blushes of different hues are to be noticed passing over the surface. These are due to the presence of numerous con- tractile, pigment-containing cells or chromatophores, situated in the deeper layers of the integument over the entire. 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 Parker, T. Jeffery (Thomas Jeffery), 1850-1897; Haswell, William A. (William Aitcheson), 1854-1925. New York, The Macmillan Company; London, Macmillan & Co. ,Ltd.
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