932 KirKwoop: POLLEN-FORMATION IN CUCURBITACEAE 
The linin fibers can no longer be distinguished as such, having 
been merged with those from the cytoplasm. The spindle now 
becomes bipolar, and the interpolar fibers are brought out in sharp 
contrast to the others by their stronger absorption of the stain. 
Three kinds of fibers were visible: the mantle-fibers which run 
out from the poles of the spindle into the cytoplasm toward the 
equatorial region; the fibers which attach to the chromosomes 
and appear to draw them to the poles; and the interpolar fibers 
which occupy the center of the spindle and are easily distinguished 
throughout the anaphase and telophase. All of these except the 
contractile fibers are of a more or less sinuous form. The inter- 
polar fibers are considerably thicker in their middle region, and 
such parts are colored quite darkly by the haematoxylon stain. 
During the first division the poles of the spindle do not seem to- 
reach the peripheral cytoplasmic membrane but terminate at some 
distance from it (FIGURE 28). Outside of the space occupied by 
the spindle itself the cytoplasm is of a densely granular character, 
but even in relatively thin sections (3 4) no extensions of the 
spindle to the ‘‘H/autschicht” could be seen. 
The conception of an anchorage for the spindle by kinoplasmic 
fibers extending to the outer membrane, as expressed by Stras- 
burger,‘ seems here hardly to be justified. It seems apparent, 
however, that the mantle-fibers may fix the spindle in its position 
by a connection with the cytoplasmic reticulum. The necessity 
for the fixation of the poles of the spindle in the Hautschicht, in 
order to facilitate the drawing apart of the chromosomes by con- 
traction of the fibers, is not quite apparent. It is suggested that 
the interpolar fibers may act as a sort of stay, which, with a certain 
degree of rigidity, would facilitate the separation of the chromo- 
somes by the contraction of the overlying fibers. The evidence 
at hand as to the character of the interpolar fibers certainly favors 
such a view. 
The spindle of the second division originates like that of the 
first and is also multipolar in its early stages. The fibers of the 
cytoplasmic kinoplasm traverse the nuclear vacuole and soon 
obliterate it. No evidence ‘could be found at any time of a fe 
ticulum next the nuclear wall. The spindle forms from the kino- 
plasmic fibers which grow in from the cytoplasm. The spindle- 
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