722 THE AMERICAN NATURALIST. (Vor. XXXIX. 
(Davis, :01, p. 171) are outlined the changes in form which 
kinoplasm may assume in the mitoses of the liverworts upon 
which is based a theory of a cycle through which kinoplasm 
may run in the history of a cell. On this theory, centrosphere, 
polar cap, and the free fibrillar condition are all secondary devel- 
opments from a primal finely granular kinoplasm which is the 
only form of kinoplasm that is in any sense permanent in the 
cell. This finely granular kinoplasm is always present in char- 
acteristic form in the plasma membranes of the cell. The sub- 
stance of centrospheres, polar caps, and fibrille arises from 
accumulations of granular kinoplasm during prophase and these 
Structures return to the same undifferentiated granular kino-: 
plasm at the end of mitosis or become lost in the general 
cytoplasm of the cell. : 
The cycle is from an undifferentiated finely granular kino- 
plasm through certain specialized conditions either wholly or 
in part fibrillar in structure back to the granular state. The 
centrosphere and polar cap are regions from which fibrillz de- 
velop at least in part and to which they may remain attached as 
to an anchorage. The polar cap is a less clearly differentiated 
kinoplasmic center than the centrosphere but does not differ . 
from it in the essentials of its organization. It seems to me that 
the two structures are very closely related in the liverworts and 
that in this group we may readily conceive the polar cap as de- 
rived from the centrosphere. The free fibrillar type of spindle 
formation is a step farther in the direction of such a distribution 
of the kinoplasm that no very positive centers for the develop- 
ment of the spindles may be distinguished. The four-rayed 
structure (quadripolar spindle) so characteristic of- the spore 
mother-cell in the Jungermanniales represents a group of four 
temporary centers for the formation of fibrille and there is 
clearly a gathering of kinoplasm at these points but the regions 
are so vague in outline as hardly to justify the designation of 
centrospheres. From the fibrillar state, kinoplasm returns to 
the finely granular condition by the contraction of the fibers 
w pepanen ops to some common area. 
nuce We DEL e chromosomes of the daughter 
er in part at least a nuclear mem- 
