1906] OLIVE—NUCLEAR AND CELL DIVISION OF EMPUSA 249 
achromatic substance remaining between the separated chromosomes, 
e. g., in KruTen’s fig. zz. But in Empusa, there is no appreciable 
achromatic substance in the corresponding equatorial region of figs. 
62, 67. There is, therefore, according to my interpretation, in the 
simple cases where no equatorial arrangement of the chromatin takes 
place, practically no development of a central spindle; but whether 
these two facts are related somehow as cause and effect must await 
further investigation. Hence we may regard the intranuclear figure 
in the case of Empusa and Coccidium, as an extremely simple 
apparatus, which consists merely of the two opposed centers of divi- 
sion, each with its system of polar radiations. Further, these polar 
rays must all correspond in function to the mantle-fibers, instead of 
in part to the extranuclear polar asters of the higher animals, since 
they all mark the paths of movement of chromatin material. As 
seen in figs. 50, 54, 55, 59, for example, the fact is quite apparent that 
the intranuculear centrosomes lie some distance from the nuclear 
membrane, and that there is no appreciable differentiation in the 
radiations which extend in all directions from them. All appear 
alike to consist, at least in part, of chromatin material. In later 
stages, represented in figs. 64, 65, the centers appear to have been 
pulled to the periphery so that they come to lie against the nuclear 
membrane. I am inclined to think that this peripheral position 
represents the ultimate fate of all of the centrosomes, since the very 
last stages (e. g., fig. 6r) almost invariably show the old centers lying 
at one side against the nuclear membrane. Such figures lead us to 
believe that after all there may be a slight differentiation in the astral 
radiations, since those fibers which attach the centrosome to the 
nuclear membrane may be mainly concerned in this peripheral move- 
ment of the centers, forming in these instances a sort of “antipodal 
cone” of fibers. At any rate, while there may be, in such a spindle, 
certain polar structures which appear to have a special function and 
thus to form an “antipodal cone,” there is no such striking differen- 
tiation of the aster into a “principal cone” and “polar rays”’ as was 
described by VAN BENEDEN. 
In those more complicated centronuclei in which the chromatin is 
gathered during nuclear division into an equatorial plate and in which 
definite* chromosomes are formed, as in Euglypha, Paramoecium, and 
