1898] CENTROSOMES IN PLANTS 159 
then reorganized before the division of the nucleus. It is 
formed of that substance which certain authors have called 
achoplasm, or kinoplasm, in order to distinguish it from the 
wutritive protoplasm or trophoplasm. It can be said in a general 
way, therefore, that the centrosome is the fundamental element 
ofthe sphere, since often it alone persists, and it is the centro- 
some which has the greatest affinity for staining fluids. However, 
itis known that in certain cases, observed especially by Van der 
Strich and von Rath, the attractive sphere conceals the centro- 
some, but one is not justified perhaps in concluding that the 
latter element is in such a case completely absent. 
Some observers have asserted, also, that the centrosomes and 
the Spheres have no distinct existence, but are appearances 
fesulting from certain activities of the protoplasm. 
It does not seem possible at present to characterize the cen- 
Seomes by their composition, or by the manner in which they 
|. © Mi Tespect to stains. Yet Heidenhain, and other authors 
“aim that the centrosomes are composed of a particular chemi- 
__ {al substance; while Viessing thinks that to find the specific 
€t of these bodies it is necessary to study, not their 
Composition, but their position in the center of a pro- 
tadiation which they serve as a point of attachment. 
| thesia! animal cell there has been observed a single 
ae ne two neighboring centrosomes, some- 
— centrosomes lying side by side and forming 
Tn this last —. % Heidenhain, or the “centriole” of Boveri. 
of € the typical centrosome is replaced by a group 
hanules, which divides, lik ical trosome, into two 
atthe beginnin at ) “ed e . typical centrosome, 
| ten the : nuclear division. a 
the moment ness very small and scarcely visible at 
Process divide oe division, increase in size during that 
ir former co - ae time as the nucleus, and then return 
Me several See ition and cease to be recognizable. There 
es Permanent ts, however, who do not conniges the tentee 
"© Majorit pr eans a the cell, but such is not the opinion 
y of zoologists, who have observed centrosomes 
