The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . ed with consider-able force through the atrialaperture. The current of p^^ ^water passing in is for re- side,spiratory purposes, and italso conveys food into the animal. The atrial current ismainly the water which has been used in respiration, butIt also contains all excretions from the body, and at timesthe ova and spermatozoa or the »!t The outer grey fiart of the
The Encyclopedia britannica; a dictionary of arts, sciences, and general literatureWith new maps, and original American articles by eminent writersWith American revisions and additions, bringing each volume up to date . ed with consider-able force through the atrialaperture. The current of p^^ ^water passing in is for re- side,spiratory purposes, and italso conveys food into the animal. The atrial current ismainly the water which has been used in respiration, butIt also contains all excretions from the body, and at timesthe ova and spermatozoa or the »!t The outer grey fiart of the body, which is attached ator near its posterior end and penetrated by the two aper-tures, is the test. This is a firm gelatinous cuticularsecretion from the outer surface of the ectoderm, which isd layer of flat cells lining its inner surface. Although atfirst produced as a cuticle, the test soon becomes organizedby the migration into it of cells derived from the ectoderm(see fig. 2). These tost cells may remain- as rounded orfusiform or stellate cells imbedded in the gelatinous matrix,to which they are constantly adding by secretions on their * Some writers use a different uonienclature of regions ; see (77).. Ascidki mtntula from tlie rightat, atrial aperture ; br, biaochiaLaperture ; (, test. (Ongin-il.) bloi.
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Keywords: ., bookcentury1800, bookdecade1890, bookidencyclopedia, bookyear1892
