664 Graham. — Nuclear Division of Preissia commutat'd . 
ground that it is an artifact, due to faulty fixing. Cells in all other phases 
of division lie near those in which the spireme is contracting about the 
nucleolus, and no evidence of faulty fixing can be observed. Cells showing 
a recovery of the spireme from the contracting state lie in the growing 
region, and cannot be explained on the assumption that this contraction is 
an artifact. 
At early prophase, when the nucleus is elongated, the cytoplasm 
becomes massed at the ends of the nucleus. These masses are dense and 
contain numerous granules. They are closely applied to the membrane 
of the nucleus at its ends (Figs. 2, 3). These granular masses may be 
found applied to the nuclear membrane at the ends of all nuclei in early 
prophase (Figs. 4, 5, 6 are not cut parallel with the long axis of the 
nucleus). Between the granular cap and the nuclear membrane there now 
appears a cone-shaped hyaline cap that rests on the ends of the nucleus. 
The boundary of the hyaline polar cap presents a sharp outline which may 
be pointed or blunt at its apex (Figs. 11, 12). This boundary appears 
slightly granular in cross-section. The granular areas are not so prominent 
after the appearance of the hyaline caps (Figs. 11, 12). Whether part 
of the granular area of cytoplasm is transformed into a hyaline substance 
that forms the hyaline caps, or the caps are composed of a hyaline fluid 
that is extruded from the nucleus, was not determined. In cells in the root 
of Hyacinthus orientalis , Rosen (’ 95 ) found a layer of hyaline kinoplasm 
surrounding the nucleus. Later the kinoplasm does not envelop the nucleus, 
but appears on opposite sides of the nucleus at the elongated ends as polar 
caps. Their appearance in Rosen’s material and in Preissia commutata is 
similar at this later stage. Rosen (’ 95 ) believes that the substance of the 
cap is derived from the cytoplasm. Nemec (’ 99 ) describes hyaline caps 
in the vegetative cells of Vicia Faba and several other Seed Plants. He 
also described an enveloping layer of hyaline kinoplasm around the nucleus 
that later takes the form of polar caps. He believes that this substance 
surrounding the nucleus, and later forming the caps, is identical in chemical 
peculiarities with the nuclear sap. Nemec’s (’ 99 ) experiments show that 
the form of the hyaline polar caps is due to a force pulling them in the 
direction of the long axis of the nucleus. By chloroforming or plasmolysing 
the living tissue, the hyaline polar caps return to the form of a hollow 
sphere surrounding the nucleus. In Preissia commutata the spindle fibres 
are developed in the hyaline polar caps. These fibres have a finely granular 
appearance. When the spireme is segmenting to form chromosomes, spindle 
fibres are being formed in the hyaline polar caps (Fig. 13). These fibres 
converge at the apex of the cap (Fig. 14). The form of the polar cap after 
the development of the fibres is unchanged. Sections showing the develop- 
ment of the fibres, in which the outline of the cap of granular fibres presents 
a blunt appearance, such as Rosen (’ 95 ) illustrates in his Fig. 3 c, were not 
