- 
1894. ] Attraction-Spheres and Centrosomes. 455 
ceeding stages of the division (figs. 8-10), and through the 
resting stage of the nucleus until a new division of the nucleus 
takes place. | 
It will be seen from the fact that the centrosomes remain 
at the position of the pole of the daughter nucleus until the 
division following, that in the case where the next spindle is 
inthe same direction as the preceding one, one of the cen- 
trosomes must travel through 180° to come to the opposite 
pole of the nucleus. But in the case where the division is at 
right angles to the preceding one, each centrosome must 
travel through 45° in order to reach the poles of the future 
spindle. Now in the Allium root tips, in many cases, ina 
given chain of cells, division will take place logitudinally at 
4 certain distance from the apex; and from that point onward 
there will be two chains of cells instead of one, and farther 
on the division of the nucleus will again be in a plane trans- 
verse to the axis of the root. Thus taking such an example 
where the cell has divided transversely, if the next division — 
Slongitudinal each centrosome must pass through 45°; the 
ixt division being transverse again both bodies must again 
"avel as before; but in the third division one of the bodies 
will be stationary while the other passes through 180°. Ina 
strand of cells coming from the apex of the root, the cells as 
fy continue to divide always maintain a curve, and the 
attraction-spheres will not be quite 180° apart as they lie at 
the two poles of a dividing nucleus. I have observed in cells 
t these points, that the spheres lay inclined with the daugh- 
ter nucleus toward the concave side of the strand of cells. 
The bodies do not always travel in the same direction, as will 
feadily be seen when we take into consideration a strand of 
Cells from an onion root whose elements are dividing trans- 
Yersely, If the spheres are at the proximal end of the nucleus 
» When division occurs, the migrating one will travel in a direc- 
ae foward the apex of the root; but if they lie at the distal 
Tf the nucleus it must travel in the opposite direction. 
if whole subject shows that the centrosomes with their 
ah  cavel in a very complicated manner during the for- 
on of any given vegetable tissue. 
2 very pesalas shereeneie was noticed in the root a 
in ‘ium, In many cases the spindle was formed obliquely 
ci +9 cell, the attraction spheres lying near opposite corners 
me cell as it appeared in longitudinal section (fig. 11), 
