1912] : GRIGGS—RHODOCHYTRIUM 153 
thereby drawing attention to the laggard. Coincident with the 
appearance of these kinoplasmic fibers the chains of chromatin 
usually break up, and the individual masses become more definitely 
spherical, karyosome-like structures. In a nucleus a little further 
advanced the fibers have become more abundant and permeate all 
parts of the nuclear cavity (fig. 49), and on some of them are seen 
small deeply staining granules whose origin, fate, and function are 
not altogether clear to me. 
From the very first the position . one of the poles of the future 
spindle can be recognized in the focus of certain of the fibers 
(figs. 48-50). Curiously enough, however, the other pole does not 
seem to appear until somewhat later, so that the young spindles 
show a considerable difference in the two poles, one being more 
fully formed than the other (fig. 51). This is such a peculiar 
phenomenon that one is strongly inclined to believe, when he finds 
such a nucleus, that he has overlooked the opposite pole on another 
section (most of the spindles are of course somewhat oblique), but 
careful search almost invariably failed to reveal it. Fig. 50, which 
is a sagittal section of a primary nucleus, shows perhaps the extreme 
of this condition; notwithstanding the strong development of 
kinoplasmic fibers in the part of the nucleus drawn, they were 
entirely absent from the other parts. It is quite possible that the 
spindles seen in these stages were unusual, but the occurrence of 
the unipolar condition in different pieces of material killed in 
different years has convinced me, against my prejudices, that this 
is a normal and usual method of spindle formation. 
Such a drawing as fig. 50 resembles the prophase in the Ascomy- 
cetes, in which the linin strands containing the chromatin radiate 
from one side of the nucleus. There are, however, important 
differences between the two. The polarity of the ascomycetous 
spindle is determined by the presence of centrosomes attached to 
the nuclear membrane, but in Rhodochytrium no centrosomes are 
visible, and the pole does not necessarily touch the nuclear mem- 
brane at all. The origin of the bipolar condition is entirely dis- 
similar. In the Ascomycetes the two centrosomes, derived from 
the fission of one, separate and migrate to opposite sides of the 
nucleus, each carrying with it its quota of fibers with attached 
