BEHAVIOUR OF THE NUCLEUS IN DIVISION. 103 



more or less linear extended filaments are usually connected at their ends ; now and 

 again they become connected also at other points by cross bridges. Later, in cell- 

 nuclei poor in contents (i. e. containing little nuclein), the individual filaments become 

 drawn together in such a manner, that they form a simple layer of rodlets or granules 

 in the equatorial plane. If the filaments were fused at their polar ends, this con- 

 nection is first loosened. In cell-nuclei rich in contents (i.e. rich in nuclein) the 

 filaments also maintain a considerable length in the stage now treated of, and they 

 may even reach from the one pole of the nucleus to the other. In nuclear figures 

 with equatorial bridges, the loops open, not only in the filaments turned towards 

 the poles but also in those lying equatorially. The equatorial connecting filaments 

 hereupon resolve themselves chiefly into V-shaped figures placed radially with the 

 free legs directed outwttrds. The filaments directed towards the poles become 

 more or less drawn towards the equator and at the same time shortened, or they 

 maintain their original lengths. They converge somewhat towards the poles, 

 or run almost parallel to one another, or curve, even spreading' strongly out- 

 wards from one another. In the formation of the nuclear figure described, the 

 whole stainable substance (the nuclein) of the cell -nucleus is demonstrably 

 employed^.' 



Strasburger distinguishes this everywhere as thenuclear disc. This consists 

 therefore in the simplest case of a simple layer of granules or of straight parallel 

 rodlets. These elements are visibly separated from one another; and, looked at 

 from pne of the nuclear poles, a radial arrangement is sometimes to be discovered, 

 sometimes not. The rodlets of the nuclear disc (the nuclein rodlets) may, how- 

 ever, also be of more considerable length, and at the same time be curved in an 

 irregular manner, spreading very much towards the exterior. On both sides 

 of the nuclear disc, in the great majority of cases, delicate fibrillse are visible 

 which (with colouring media such as hsematoxylin) are generally stained only 

 faintly or not at all. These are the so-called spindle strias or fibrillas of 

 Strasburger. 



' These form together with the nuclear disc (the described arrangement of 

 the nuclein) the nuclear spindle. The spindle fibrillse show themselves most beau- 

 tifully and plainly when the nuclear disc is limited to only one equatorial layer of 

 granules or rodlets. They are so much the less visible the greater the extension 

 of the nuclear disc (i. e. again the nuclein rods) towards the poles.' The so-called 

 spindle fibrillse of Strasburger are, according to his view, formed from the substance 

 of the surrounding protoplasm, or they belong, as we may w-ell assume, to the 

 ground substance of the cell-nucleus, the niicleo-plasma. ' Since now the formation 

 of the spindle fibrillae,' says Strasburger, ' starts from the two poles of the cell- 

 nucleus and proceeds towards the equator, the continuous spindle fibrillae, which 

 can be traced between the elements of the nuclear disc (the rodlets of nuclein) from 

 one pole to another, can only have originated by fusion of the ends meeting one 

 another. Other spindle fibrillae join the elements of the nuclear disc (the nuclein 

 rodlets) on both sides. 



■ 1 The staining of the nuclein is brought about especially by means of haematoxylin, with the 

 aid of picric-acid, alum, and other reagents. Compare the works mentioned in note 2, p. loi. 



