154 BOTANICAL GAZETTE [FEBRUARY 
chromatin. But in Rhodochytrium the second pole is formed, like 
the first, by the convergence of certain fibers to a point. In nuclei 
a little older than that shown in fig. 50, some of the kinoplasmic 
fibers can be seen to intersect at points more or less directly opposite 
the first pole. There are usually two or three such points (fig. 51), 
from each of which a few fibers radiate. In later stages one of 
these focal points becomes more prominent than the others, until 
ultimately it becomes the second pole of the spindle, as prominent 
and definite as the first. 
In the fully formed spindle the larger proportion of the fibers 
of course stretch from pole to pole, but in the early stages the rays 
from each pole appear as an independent fascicle radiating from 
the focus, with little regard to the position of the opposite pole. 
The vestiges of this condition may be seen in fully formed spindles, 
in which many of the acicular mantle fibers stretch straight by the 
equator of the spindle, intersecting those from the opposite pole 
(figs. 52-54). Not infrequently a few fibers center in the pole and 
do not enter into the formation of the spindle, but radiate into the 
nuclear cavity. In one instance such radiations were so numerous 
as to give the appearance of a conspicuous aster (fig. 53). But 
comparison with the opposite pole shows that the effect here 
produced is largely accidental. Nothing similar was seen elsewhere. 
Chromosome formation.—The differentiation of the chromosomes, 
in my material, is a much more difficult matter to follow than the 
formation of the spindle. Of the masses of chromatin which are 
distributed throughout the nuclear cavity, part remain free and 
part become connected with the developing spindle fibers. In 
addition to these, some of the spindle fibers, especially in the early 
stages, are studded with smaller chromatic granules whose sig- 
nificance, as stated above, is obscure to me. At one stage of the 
investigation I was inclined to believe that these were used in the 
formation of the chromosomes, but further observation has led me 
to the conclusion that it is the large chromatin masses which give 
rise to the chromosomes. Whether the chromosomes are derived 
exclusively from the latter is not certain, but such figures as no. 5! 
show at least that some of them are utilized in chromosome 
formation. 
