. Elements of comparative zoology. Zoology. Phylum I.—SPONGIDA (Porifera). Sponges differ from other animals in so many respects that for a long time naturalists were uncertain as to whether they were animals or plants, but this matter has long been settled beyond dispute. There is, however, more ques- 0 tion as to the position of these forms in the Animal Kingdom. They have been regarded as colonial Protozoa, as members of the Ccelenterata, and as a distinct group, or phylum, the position given them here. The structure of a sponge can be best understood by starting with the simplest forms (fi
. Elements of comparative zoology. Zoology. Phylum I.—SPONGIDA (Porifera). Sponges differ from other animals in so many respects that for a long time naturalists were uncertain as to whether they were animals or plants, but this matter has long been settled beyond dispute. There is, however, more ques- 0 tion as to the position of these forms in the Animal Kingdom. They have been regarded as colonial Protozoa, as members of the Ccelenterata, and as a distinct group, or phylum, the position given them here. The structure of a sponge can be best understood by starting with the simplest forms (fig. 10). One of these is a vase-like structure with a central or gastral cavity communicating with the exterior by a terminal opening, the osculum. Through the sides of the vase are numerous small openings or pores (whencethe name Porifera), and through these water, carrying with it oxygen and small food particles, is drawn, the waste-water passing from the gastral cavity by means of the osculum. Such a sponge is the so-called Ascon type. If now the gastral cavity develop pouch-like folds in 158. Fig. 10. — A simple (Olynthus) sponge (after Haeckel). One side has been broken away to show the interior, e, spicules; i, eggs; o, osculum; p, pores; u, gastral 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 Kingsley, J. S. (John Sterling), 1854-1929. New York, H. Holt and Company
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1904
