724 THE AMERICAN NATURALIST. [Vor. XXXIX. 
developed entirely out of the cytoplasmic network. The au- 
thors are unable to distinguish a kinoplasm distinct from the 
general network of the cell. These are vital points of differ- 
ence which are fundamental to the understanding of mitotic 
phenomena and rest of course on matters of fact. The chief 
points at issue concern the structure and development of the 
asters and the nature of the material at their centers. My own 
studies and those of Farmer and Chamberlain have convinced 
me that there is an accumulation of substance (kinoplasm) in 
the centers of the asters and polar caps to such an amount that 
. it must be regarded as a definite structure in the cell and its 
morphology and relations to the spindle have certainly justified 
us in considering it as similar to the centrosphere of the thallo- 
phytes. 
4. THE EssENTIAL STRUCTURES IN THE PLANT CELL AND 
THEIR BEHAVIOR IN ONTOGENY. 
grouped as cytoplasmic and nuclear. The greater part of the 
cytoplasm, including that which is ter 
organization peculiar to itself and v 
the plasma membranes. This Structure has been described as 
alveolar or of the nature of foam and sometimes fibrillar and 
with various large granular inclusions. The cytoplasm also con- 
tains the characteristic organs termed plastids. The conspicu- 
ous structures of the nucleus aré: the chromatic elements 
med trophoplasm, has an 
ery different from that of 
