Outlines of zoology . large exhalant aperture [psculuni), but in other cases there are many exhalant delicate outer layer covers the body, and is perhaps continued into the affer-ent canals. Beneath the covering layer there is in all but the simplest forms a mass of cells (the ) which may be very varied in its composition. Thus th^re are scleroblasts maki?ig the skeleton of lime, flint, orspongin ; amxboid cells or phago-cytes, important in digestion andexcretion , reproductive cells, andother ele?nents. This median mass of cells istraversed by the afferent canalsand by t
Outlines of zoology . large exhalant aperture [psculuni), but in other cases there are many exhalant delicate outer layer covers the body, and is perhaps continued into the affer-ent canals. Beneath the covering layer there is in all but the simplest forms a mass of cells (the ) which may be very varied in its composition. Thus th^re are scleroblasts maki?ig the skeleton of lime, flint, orspongin ; amxboid cells or phago-cytes, important in digestion andexcretion , reproductive cells, andother ele?nents. This median mass of cells istraversed by the afferent canalsand by the diverticula of thecentral cavity or the branches ofthe original central cavity, linedby flagellate cells. It is difficultto call this cavity or system of cavities the gut or enteron, or to call the layer which lines if the endoderm, or the outer covering layer the ectoderm. In Fig. 56.—Simplesponge [Ascetlaprimordialis),—After Haeckel. Note the vase-like form,the apical osculiinij theinhalant pores in Fig. 57.—A sponge colony. 126 PHYLUM FORI PER A SPONGES.
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu3192, booksubjectzoology
