The porifera and coelentera . emainat a lower stage of elaboration. In su))i)ort of the theory here put forward, it maybe pointed out that the porocytes of Calcarea entrap and ingest larger bodies, sucli IHatonis, whicli are often to be found in them. so SPONGES nucleus as a minute s{)lierule easily distinguished by its stainingproperties from the ordinary cell granules. The spherule grows inlength and becomes a rod. The rods of neighbouring cells in eachstring unite to form a jointed fibre, each segment being separatedfrom the next by an intervening substance less resistent to acidsand alkali
The porifera and coelentera . emainat a lower stage of elaboration. In su))i)ort of the theory here put forward, it maybe pointed out that the porocytes of Calcarea entrap and ingest larger bodies, sucli IHatonis, whicli are often to be found in them. so SPONGES nucleus as a minute s{)lierule easily distinguished by its stainingproperties from the ordinary cell granules. The spherule grows inlength and becomes a rod. The rods of neighbouring cells in eachstring unite to form a jointed fibre, each segment being separatedfrom the next by an intervening substance less resistent to acidsand alkalis (Fig. 51, B). The secreting cells next become spindle-shaped, and their contained rods become in consequence elongatedand drawn out (Fig. 51, C and D). At the same time, theirsubstance acquires a denser consistence, more tenacious and lesssoft The result is a slender fibril, in which the segmentationgradually ceases to be visible, enclosed in a protoplasmic this process the secreting cells gradually lose their. ?), after Loisel. A, sjxmgoblasts, each containing a minute, rod-like body,dispostxi invjinlarly at n, arranj;e<l in a row at . the rods are uniting end to end to forma jointed tibril. (, later stage, the rods more elongate, and the cells now almost free fromspherules. /), tibril continuous, cells coMinienciiig to degenerate. K^ fully formeii tibril, withadherent cell remnants ; n, luiclei. spherules until they are left with a clear cytoplasm and nucleus(Fig. 51, £?). Finally, the fibrils come to lie free in the parenchyma,losing their enveloping cells, the nuclei of which appear to becomescattered in the ground substance. The whole process of fibrilformation is thus comparable to the secretion of the spicules, eachjoint being formed in precisely the same manner as a single monaxonspicule, while the whole fibril represents a number of s
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Keywords: ., bookcentury1900, bookdecade1900, booksubje, booksubjectctenophora
