466 The American Naturalist. [June, 
for additional observations see Prenant, 85, and Platner, 34a. 
The sphere of attraction divides, as does also its central 
body, and its two parts move to opposite sides of the nucleus. 
There thus appear two opposite accumulations of clear pro- 
toplasm, from each of which as a centre, astral rays or radiat- 
ing lines are formed in the cell-body. Meanwhile, within the 
nucleus, changes go on ; the threads of the intranuclear net- 
work radiate out from the the pole where the sphere of attrac- 
tion lies before its division, and the chromatic substance forms 
a number of distinct grains. When the sphere of attraction 
divides and its halves go asunder, the nuclear substance pre- 
serves its radiating relation to each sphere, and as the mem- 
brane of the nucleus disappears during these changes, the filial 
result of the transformation of the nucleus is a spindle-shaped 
body, the points of which rest just within the clear centre of 
each astral system, so that the spindle stretches from one pro- 
toplasmic mass to the other. The spindle consists of fine 
threads extending from pole to pole and having almost no 
affinity for the dyes of the histologist, a peculiarity which 
causes them to be known as the achromatic threads. These 
threads are probably always compounded of a considerable 
number of exceedingly fine fibrillae, see Rabl, 38, 21-22. 
The colorable substance forms a number of separate grains, 
each of which is united with one of the achromatic threads, 
and all of which lie at the same level in the centre of the 
spindle ; when the spindle is seen from the side, the chro- 
matine grains appear to constitute a central band or disc 
(Strassburger's Kernplatte) but when the spindle is seen end- 
wise, the separate grains are at once recognized. The shape 
of the grains is variable; some authors, without sufficient ob- 
servational proof, have advanced the opinion that the grains 
are ahvays V-shaped. The spindle together with the polar 
accumulations of protoplasm and the two accompanying radia- 
The domain of the radiation extends, the two protoplasmatic 
centres move further apart, the nuclear spindle elongates cor- 
respondingly, and the chromatic grains of the Kernplatte 
