1906] OLIVE—NUCLEAR AND CELL DIVISION OF EMPUSA 251 
of fibers in this region has taken place. But I can see no evidence in 
this instance of a using up of any of the material which has accumu- 
lated about the poles, as has been suggested by STRASBURGER (:00) 
to explain the shortening of the mantle-fibers in certain cases. 
It may be pointed out in this connection that the fact that the 
fibrillar radiations in Empusa appear to be almost homogenous, and 
further, chromatic in their staining reactions instead of achromatic, 
does not seriously detract from the reasonableness of the contractile 
hypothesis, as applied to this form, since it is only necessary to assume 
that contractile linin is also present in small amount in the fibers, 
along with chromatin. WHuLSON (’95), in fact, maintains that in the 
case of echinoderm eggs, the fibers are derived not merely from the 
linin-substance, but also from the chromatin. 
As in the telophases of mitotic processes in general, in the ‘Nite 
stages in Empusa a centrifugal movement of the chromatin sets in, 
which may sometimes begin even before the two daughter-nuclei are 
separated by constriction from eachother. Fig. 59 shows such a late 
condition, in which the chromatin-movement seems to be of the 
nature of an active outward growth, since we now note at the distal 
ends of the fibers accumulations of darker and apparently denser 
material. Should we assume that the aggregation of chromatin 
about the centrosome in the first instance is brought about by the 
contractility of the kinoplasm in the radiations, then we must sup- 
pose that later some subtle change occurs in the body of the 
centrosome itself, or else in the fibrillar rays, to stop contraction 
and to set up an opposite growth of the fibers. But I should regard 
it as not an impossible assumption that the centrifugal movement in 
the latter instance might be brought about simply by a loosening 
up the chromatin in the increasing nuclear sap by which it is sur- 
rounded—a phenomenon which would probably follow as a mere 
mechanical consequence the final cessation of the forces which 
caused the centripetal movement. 
The suggestion that these alternating centripetal and centrifugal 
movements of the chromatin are of the nature of flowing movements 
appears to gain some support in the case of Empusa. MONTGOMERY 
(:01, p. 352) concludes that this flowing movement of the nuclear 
materials is automatic; but I fail to see how this author can retain, 
