208 W. WALDEYER. 
ascribe to the nucleoplasm alone the active réle. The remarkable 
behaviour of the chromatic elements during fertilization must 
especially be referred to: but about these we shall speak in 
greater detail below. 
Many things distinctly point to our regarding the poles of 
the spindle figure, as well as the attraction spheres of van 
Beneden (Richtungsonnen of Kultschitzky) as very significant 
points, we would prefer to say “centres,” for karyokinetic 
phenomena: nearly all who have dealt with the subject have 
acknowledged this. But I would give a caution against 
lulling ourselves into the delusion that all the essentials 
are known, and that we can now, from this point of view, 
include the whole of the phenomena in a theory, and account 
for them uniformly. The very different views held by 
authors who all acknowledge the pole as full of signifi- 
cance, show that at present this is still impossible. With 
Flemming and Rabl I think that the time has not yet come 
when we can formulate a satisfactory theoretical conception 
of karyokinesis. 
There is one point referred to by Rabl (165) which I must 
not leave unmentioned, and I connect with it a circumstance 
already emphasised. If it is true, as Rabl states, that even in 
the resting nucleus the main threads are present in typical 
form (see figs. 2, 8, 4, 12), then we must acknowledge that 
the total change of form of the karyokinetic figure may be 
simply a question of dividing the thread-substance between the 
two new cells with rapidity and strict equality. One can 
scarcely imagine a simpler solution of this problem than the 
method used by nature in karyokinesis, viz. the appearance of 
polar and antipolar areas in the resting nucleus, the typically- 
arranged chief threads drawing in their constituents emitted in 
the form of processes, and nucleoli; then their arrangement 
in a very regular figure, gathering themselves in the middle 
(division-plane) of the nucleus (mother-nucleus) : each (mother) 
thread or chromosome dividing along itself into two daughter- 
threads; the two daughter-threads arising from one mother- 
thread simply separating from one another towards opposite 
