Textbook of normal histology: including an account of the development of the tissues and of the organs . e skein. Thequestion whether theseskeins are composed of thecontortions of one longfibre, or whether they con-tain several shorter ones,has, as yet, not been defi-nitely determined; observa-tions made on the cells oflower forms, however, ren-der it not improbable thata single thread constitutesthe entire fibrils of the looseskein now separate at theirperipheral turns, so that anumber—about twenty-four (Flemming, Rabl)—of distinct loops are formed; the closedends of these are
Textbook of normal histology: including an account of the development of the tissues and of the organs . e skein. Thequestion whether theseskeins are composed of thecontortions of one longfibre, or whether they con-tain several shorter ones,has, as yet, not been defi-nitely determined; observa-tions made on the cells oflower forms, however, ren-der it not improbable thata single thread constitutesthe entire fibrils of the looseskein now separate at theirperipheral turns, so that anumber—about twenty-four (Flemming, Rabl)—of distinct loops are formed; the closedends of these are directed towards a common centre, around which,but removed some little distance, they become arranged. Theenclosed clear space is the polar field. During the formation ofthe skeins the nuclear membrane disappears, its former positionbeing marked for some time longer by a clear zone or halo surround-ing the nucleus and defining the boundary of the latter from thecell-contents. Coincidently with the formation of the loose skein,delicate striae make their appearance within the nucleus, so disposed. Close skein,—diagram ofnuclear fibrils: A, seenfrom the side; B, from thepolar field, P; C, fromanti-pole, GP. (After Rabl-Schiefferdecker.) Loose skein : nuclear spin-dle has appeared in polarfield, P. (After Rabl-Schief-ferdecker.) THE CELL AXD THE TISSUES. 17 that together they present a double cone, whose apices are directedtowards the poles of the future new nuclei, as determined by thenew centrosomes, surrounded by the attraction spheres, now knownas the polar striation ,• these acromatin figures constitute the nu-clear spindle. The chromatin fibrils grow thicker and, at thesame time, shorter, and arrange themselves so that the closed endsof the loops encircle the polar field, giving rise, when seen from itssurface, to the wreath; seen from the side, however, the loops or Vsappear as radiating fibrils, and constitute the (4) Mother-star, or aster: the apparent differences
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