1906] OLIVE—NUCLEAR AND CELL DIVISION OF EMPUSA 257 
although they appear to be chromatic in their staining reactions, they 
probably are made up principally of chromatin, and a small amount 
of linin. The chromatin at first concentrates about the centrosomes, 
which thus appear to have a darker rim about a lighter center. The 
centripetal movement, as well as the later centrifugal movement 
characteristic of the telophases, may be regarded as of the nature of 
the flowing or diffusion of a liquid chromatin through a contractile 
linin basis. 
In the nuclear division of Empusa sciarae, the chromatin does 
not appear to pass through an equatorial plate stage. 
We may distinguish two shapes of the dividing nuclei in Empusa: 
one found in short cells of the vegetative hyphae, in which the nuclei 
in the later stages of division assume an oval or ellipsoidal shape; 
and another found in long cells, in which the nuclei become them- 
selves greatly elongated and early assume a constricted, hour-glass 
shape. In the oval nuclei, the nuclear sap accumulates so that the 
cavity becomes turgescent; while in the elongated nuclei, the liquid 
does not accumulate, at least not to such an extent as in the first 
instance, so that the consequent encroachment of the cytoplasm 
between the two daughter-halves results in an early constriction. 
In the long cells, cyclosis is doubtless stronger than in the short 
_cells, thus bringing about in such instances a greater disturbance of 
the mitotic processes. 
3. Cell-division—Cell-division in Empusa sciarae is accom- 
plished by means of the growth inward, from the wall of the mother- 
cell, of a ring-formed partition. In a majority of cases, the new cell- 
wall is carried across a wide, central, vacuolar space; when the older 
cells become filled with cytoplasm, however, and later when the 
conidium is abstricted, the wall cuts through the protoplasm which 
fills the cell. A ring-formed cleavage-furrow starts at a definite 
region of the plasma-membrane, and a wall is at once deposited in 
the cleft. A region of some thickness at the inner margin of the 
cleft, where the processes are most active which lead to the cleavage 
of the in-pushing plasma-membrane and to the deposition of the 
Partition wall, stains darker than the surrounding cytoplasm. This 
fact is made the basis for the conclusion that the split plasma-mem- 
brane is not the sole active agent of cell-division, although it may be 
