THE ARCHOPLASMIC STRUCTURES 317 



being described as having a fibrillar character.^ The same view is 

 advocated by Van Beneden in 1883. With Klein, Heitzman, and 

 Frommann he accepted the view that the intra-nuclear and extra- 

 nuclear networks were organically connected, and maintained that 

 the spindle-fibres arose from both.- "The star-like rays of the asters 

 are nothing but local differentiations of the protoplasmic network.-^ 

 . . . In my opinion the appearance of the attraction-spheres, the 

 polar corpuscle (centrosome), and the rays extending from it, includ- 

 ing the achromatic fibrils of the spindle, are the result of the appear- 

 ance in the egg-protoplasm of two centres of attraction comparable 

 to two magnetic poles. This appearance leads to a regular arrange- 

 ment of the reticulated protoplasmic fibrils and of the achromatic 

 nuclear substance with relation to the centres, in the same way that 

 a magnet produces the stellate arrangement of iron filings.""* 



This view is further developed in Van Beneden's second paper, 

 published jointly with Neyt ('87). "The spindle is nothing but a 

 differentiated portion of the asters." ^ The aster is a " radial structure 

 of the cell-protoplasm, whence results the image designated by the 

 name of aster." ^ The operations of cell-division are carried out 

 through the "contractility of the fibrillae of the cell-protoplasm and 

 their arrangement in a kind of radial muscular system composed of 

 antagonizing groups." ' 



An essentially similar view of the achromatic figure has been 

 advocated by many later workers. Numerous observers, such as 

 Rabl, Flemming, Carnoy, Watase, Wilson, Reinke, etc., have ob- 

 served that the astral fibres branch out peripherally into the general 

 meshwork and become perfectly continuous with its meshes, and 

 tracing the development of the aster, step by step, have concluded 

 that the rays arise by a direct progressive modification of the pre- 

 existing structure. The most extreme development of this view is 

 contained in the works of Heidenhain ('93, '94), Buhler ('95), Kosta- 

 necki and Siedlecki ('97), which are, however, only a development of 

 the ideas suggested by Rabl in a brief paper published several years 

 before. Rabl ('89, 2) suggested that neither spindle-fibres nor astral 

 rays really lose their identity in the resting cell, being only modified 

 in form to constitute the mitome or filar substance (meshwork), but 

 still being centred in the centrosome. Fission of the centrosome is 

 followed by that of the latent spindle-fibres (forming the linin- 

 network); hence each chromosome is connected by pairs of daughter- 



1 It is interesting to note that in the same place Klein anticipated the theory of fibrillar 

 contractility, both the nuclear and the cytoplasmic reticulum being regarded as contractile 

 (/.f., p. 417). 



2-83, p. 592. * '33- P- 550- 6/.^., p. 275. 



3 '83, p. 576. ^ '87, p. 263. '^ I.e., p. 280. 



