ORIGIN OF THE MI TO TIC FIGURE 



75 



plasm. These investigators agreed that the amphiaster is formed 

 under the influence of the centrosome, which by its division creates 

 two new ''centres of attraction" about which the astral systems arise, 

 and which form the foci of the entire dividing system. In them are 

 centred the fibrillae of the astral system, toward them the daughter- 



Fig. 28. Metaphase and anaphases of mitosis in cells (spermatocytes) of the salamander, 

 [DRUNER.] 



E, Metaphase. The continuous central spindle-fibres pass from pole to pole of the spindle. 

 Outside them the thin layer of contractile mantle-fibres attached to the divided chromosomes, of 

 which only two are shown. Centrosomes and asters. F. Transverse section through the mitotic 

 figure showing the ring of chromosomes surrounding the central spindle, the cut fibres of the latter 

 appearing as dots. G. Anaphase ; divergence of the daughter-chromosomes, exposing the cen- 

 tral spindle as the interzonal fibres; contractile fibres (principal cones of Van Beneden) clearly 

 shown. H. Later anaphase (dyaster of Flemming) ; the central spindle fully exposed to view; 

 mantle-fibres attached to the chromosomes. Immediately afterward the cell divides (see Fig. 29) . 



chromosomes proceed, and within their respective spheres of influ- 

 ence are formed the resulting daughter-cells. Both Van Beneden and 

 Boveri fully recognized the importance of their discovery. " We are 

 justified," said Van Beneden, " in regarding the attraction-sphere with 

 its central corpuscle as forming a permanent organ, not only of the 

 early blastomeres, but of all cells, and as constituting a cell-organ equal 



