490 ARTHUR BOLLES LEE. 
quite certain that the tendency to regard longitudinal fission 
of the segments at the equator as an essential element in 
mitotic cell division is no longer in harmony with observed 
facts. 
' The two groups of chromatic segments generally proceed to 
the poles of the achromatic figure, each segment on its par- 
ticular spindle-fibril, in the typical manner. But one remark- 
able case (testicular cells of Gidipoda cerulea, and of an 
undetermined locust) shows that it is not essential that the 
daughter-stars should proceed to the poles, and that the 
daughter-nuclei should be reconstituted there. In the cells in 
question the spindle does not elongate, but, on the contrary, 
flattens out (fig. 11). The segments, arranged in two lateral 
groups, do not travel along the spindle-fibrils, but, without 
changing place on their fibrils, are thrown to one side by the 
depression of the spindle (fig. 12; see explanation of these 
figures). The daughter-nuclei are reconstituted on points 
situated on the equatorial plane of the figure. It will be re- 
membered that in the course of his work on the maturation 
of the ovum of Ascaris, van Beneden found that in the forma- 
tion of the polar globules the plane of division passes through 
the axis of the dicentric figure, and is therefore perpendicular 
to the equator; whilst in normal karyokynesis the plane of 
division coincides with the equatorial plane, and is perpendicular 
to the axis of the figure. And van Beneden concludes that, on 
account of this striking difference, the formation of polar 
globules cannot be assimilated to karyokinetic cell division 
(‘ Rech. sur la Maturation, la Fécundation, etc.,’ 1883, p. 338). 
The above recorded observation of Carnoy seems to render this 
conclusion nugatory, and to suggest that the formation of polar 
globules, after the manner described by van Beneden, should 
rather be taken as a particular case of karyokinetic cell 
division. ) 
Reconstitution of the Chromatic Filament.—This is brought 
about by the union of the segments of the daughter-stars end 
to end. This union seems to be effected in various ways. 
U-shaped segments may simply take hands with their right and 
