A treatise on zoology . Section of test in Aristocystis, in the regionof a suture (s). Shows epistereoni (e), meso-stereom (m), and hypostereom (h). m is ])iercedby haplopores which are joined above at 2, 2.(Original diagram, magnified about 10 diam.). Fig. IV. CaMx Sedgivicld, from a recon-struction by Rouault ; aboutnat. size. Fig. V. A transverse section of a plate of Calix Murchisoni,the stroma - strands replaced by infilling matrix, thestereom dissolved away, x 6 diam. (After Rouault.) a truly calcified epistereom, but probably represents a hard epidermis ;there is little doubt that some


A treatise on zoology . Section of test in Aristocystis, in the regionof a suture (s). Shows epistereoni (e), meso-stereom (m), and hypostereom (h). m is ])iercedby haplopores which are joined above at 2, 2.(Original diagram, magnified about 10 diam.). Fig. IV. CaMx Sedgivicld, from a recon-struction by Rouault ; aboutnat. size. Fig. V. A transverse section of a plate of Calix Murchisoni,the stroma - strands replaced by infilling matrix, thestereom dissolved away, x 6 diam. (After Rouault.) a truly calcified epistereom, but probably represents a hard epidermis ;there is little doubt that some structure did actually cover the outer endsof- the canals ; {h) represents the inner layer of the integument, whichtowards the margins of each plate was often differentiated into elastic ormuscular strands, uniting adjacent plates and giving flexibility to thetheca ; if calcified, this layer would be homologous with the hypo-stereom of many Crinoids, but, as in the case of (e), there is onlypreserved to us the space which it occupied, filled with subsequentinfiltration or with iron oxide precipitated during the decomposition ofthe organic matter. The primitive features of Aristocystis are then :indefinite shape of theca, indefinite arrangement


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Keywords: ., bookcentury1900, bookdecade1900, bookpublishe, booksubjectzoology