THE CYTOPLASM 



35 



cut ends of the branching rays appear in the clearest manner, not 

 as plates but as distinct dots, from which in oblique sections the 

 ray may be traced inwards towards the centrosphere. Driiner, too, 

 figures the spindle in cross-section as consisting of rounded dots, 

 like the end of a bundle of wires, though these are connected by 

 cross-branches (Fig. 22, F). Again, the crossing of the rays pro- 

 ceeding from the asters (Fig. 69), and their behaviour in certain 

 phases of cell-division, is difficult to explain under any other than 

 the fibrillar theory. 



We must admit, however, that the network varies greatly in 



Centrosphere con- 

 taining the cen- 

 trosome. 



Aster. 



Spindle. 



Chromosomes forming the equatorial plate. 



Fig. 16. Diagram of the dividing cell, showing the mitotic figure and its relation to the cyto- 

 reticulum. 



different cells and even in different physiological phases of the 

 same cell ; and that it is impossible at present to bring it under 

 any rule of universal application. It is possible, nay probable, that 

 in one and the same cell a portion of the network may form a 

 true alveolar structure such as is described by Biitschli, while other 

 portions may, at the same time, be differentiated into actual fibres. 

 If this be true the fibrillar or alveolar structure is a matter of 

 secondary moment, and the essential features of protoplasmic organ- 

 ization must be sought in a more subtle underlying structure. 1 



1 See Chapter VI. 



