The porifera and coelentera . e radialtubes, and the outer surface of the body presents a smooth, poroussurface, so that the form and appearance of the Oli/nthus may beperfectly retained (Figs. 9, 10). In addition to these changes in the incurrent system, variousmodifications may take place in the radial tubes, or in their relationsto the gastral cavity. In the first place, the radial tubes may becomevery much branched and secondarily complicated. A more im-portant change, however, from the morphological point of view, isthe formation of an excurrent duct connecting the radial tube withthe gas
The porifera and coelentera . e radialtubes, and the outer surface of the body presents a smooth, poroussurface, so that the form and appearance of the Oli/nthus may beperfectly retained (Figs. 9, 10). In addition to these changes in the incurrent system, variousmodifications may take place in the radial tubes, or in their relationsto the gastral cavity. In the first place, the radial tubes may becomevery much branched and secondarily complicated. A more im-portant change, however, from the morphological point of view, isthe formation of an excurrent duct connecting the radial tube withthe gastral cavity—that is to say, the flagellated chamber is, as itwere, carried outwards, and does not open into the gastral cavitydirectly, but communicates Avith it by means of a short duct linedby flattened epithelium. At the same time the excurrent aperture,or apopyle, of the chambers may become greatly contracted, appear-ing as a perforation in a diaphragm separating the chamber fromits excurrent duct (cf. Fig. 67;. SPONGES.
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Keywords: ., bookcentury1900, bookdecade1900, booksubje, booksubjectctenophora
