. Elements of biology, with special reference to their rôle in the lives of animals. Biology; Zoology. 100 ELEMENTS OF BIOLOGY contains supporting rods or spicules composed in some genera o£ silicon, in others o£ a calcium salt, and in others o£ a peculiar tough substance called spongin. Some sponges are composite individuals consisting of a considerable number of subordinate individuals with the central cavities continuous. The common bath sponge is a composite individual. In its market form it is merely the spongin PORIFERA •'"^Maj^wT SPICULES INCUHKENT CANAL CENTRAL CAi'/ry. OSCULUM iE
. Elements of biology, with special reference to their rôle in the lives of animals. Biology; Zoology. 100 ELEMENTS OF BIOLOGY contains supporting rods or spicules composed in some genera o£ silicon, in others o£ a calcium salt, and in others o£ a peculiar tough substance called spongin. Some sponges are composite individuals consisting of a considerable number of subordinate individuals with the central cavities continuous. The common bath sponge is a composite individual. In its market form it is merely the spongin PORIFERA •'"^Maj^wT SPICULES INCUHKENT CANAL CENTRAL CAi'/ry. OSCULUM iEXCURHENT) ECTODERM ENOODERM FIG. 32. A SIMPLE SPONGE (WALL CUTAWAr) network of such an individual from which the tissues of the ani- mal have been removed. Phylu7n Coelenterata Members of this phylum are also composed essentially of two layers of cells enclosing a cavity, and are vase-shaped. The endoderm lines the sac-shaped cavity which serves as a digestive organ. The cavity has but a single opening, the mouth; the walls are not perforated as in the Porifera. They, like the sponges, are radially symmetrical and occur as single and as composite individuals. All members of the phylum are equipped with a peculiar type of sting-. 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 Buchanan, James William, 1888-. New York, London, Harper & brothers
Size: 1033px × 2420px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpubl, booksubjectbiology, booksubjectzoology
