File:The royal natural history (1893) (14595009660).jpg

Identifier: royalnaturalhist612lyde (find matches)
Title: The royal natural history
Year: 1893 (1890s)
Authors: Lydekker, Richard, 1849-1915 Sclater, Philip Lutley, 1829-1913 Frostick, W. B., former owner. DSI Brooks, W. T., former owner. DSI
Subjects: Zoology Natural history
Publisher: London and New York : Frederick Warne & Co.
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Smithsonian Libraries

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her with small flagellated chambers; of the latter, oftenonly one or two open into an out-current space or rootlet. The jelly mass, which in the model supports the hollow mulberry cluster andthe channels from the outer skin, would of itself form an inefficient support, so wemust add to it a scaffolding of rods and bars or tough horny fibres : the commonbath-sponge skeleton, and the skeleton of the Venus flower-basket are the hornyand flinty scaffoldings supporting the soft tissues together with the flagellatedchambers and the channels which lead to and from them in the living sponges.The fleshy or jelly substance of sponges is termed mesoderm (middle layer),because it is situated between the collar-cells, which constitute the endoderm vol. vi.—34 53° SPONGES. (inner layer), and the layer of cells on the outer surface, or ectoderm (outerlayer). The usually flat cells of the ectoderm are now considered to besimply a superficial layer of mesoderm cells, and not to constitute a special
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carpenters glass-sponge, Pheronema (nat. size). separate layer distinct in itself. Whether this be the case or nut, the termsmesoderm and ectoderm may be conveniently retained here. The ground-substance, or mesoderm, contains cells of various kinds, namely, irregularly-shaped CHAR A CTERIST1CS. 5 31 cells with slender branching processes, which unite with those of other cells toform a network; wandering amoeboid cells, probably concerned with digestion,distribution of nutriment, and excretion; skeleton-forming cells, which secretelime, or flint spicules, or horny fibres ; contractile muscle-cells, possibly nerve-cells ; and, lastly, male and female reproductive cells. The cells with the slenderprocesses secrete the gelatinous ground-substance, which may be compared to thematerial forming the umbrella of jelly-fish. The varying consistency of sponges, which may be soft, stony, leathery, horny,etc., results from the amount and kind of material secreted by cells of the mesoderm.In the Ve

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