630 MUlilEI. liOliKKTSON AND K. A. MINCIIFX. 



show the two best diaster-stages we have found. Fig. 23 

 shows the spindle well, but the cell is cut almost liorizontally, 

 and the collar and one daue:hter-flai»'elluni are sliced off : in 

 fig. 24 the cell is cut more vertically, and shows the collar, 

 but the plane of the spindle lies obliquely, and only one cen- 

 trosonie and daughter-flagellum can be made out. The scarcity 

 of the diaster-stage indicates that it is passed over very 

 rapidly, and this conclusion receives further support from 

 the fact that in the subsequent stages, when the daughter- 

 nuclei are being reconstituted, the daughter-flagella are 

 scarcely longer than tliey were in the stage with the undivided 

 equatorial plate. 



After the diaster-stage, and with the reconstitution of the 

 daughter-nuclei, the cell-body begins to divide (figs. 25-28a). 

 Between the two daughter-nuclei there are seen for a time 

 streaks, the remains of the achromatic spindle, stretching 

 across from one to the other (figs. 25-27) ; these streaks per- 

 sist nntil the division of the cell-body is far advanced. The 

 details of the reconstitution of the nuclei are difficult to make 

 out clearly ; the chromosomes appear to fuse together into a 

 compact mass in which their individuality is masked, if not 

 lost. The division of the cell is effected by means of a con- 

 striction in the vertical plane, producing a cleavage which is 

 much more marked at the upper than at the lower end of the 

 cell. The cleavage goes right through the old collar, and 

 leads to its destruction and disappearance ; it appears to 

 break down into a granular mass which disintegrates and 

 vanishes. 



When division of the cell-body is complete the new collars 

 of the daughter-cells grow out round the short but growing 

 flagella. At their first origin the new flagella projected in 

 an oblique direction from the dividing cell, as figs. 18-28 

 show clearly ; they took origin from that portion of the 

 surface of the parent-cell which lies between the flange and 

 the base of the collar. When the division is nearh* complete 

 (figs. 28a. and 47), the point of origin of the flagella becomes 

 slightly shifted so as to be placed at the uppermost level of 



