Osborn —Spongospor a subterranea , ( Wallrot/i ) Johnson. 333 
ever, is very small (7 /x), as may be seen by a comparison with that of Bad-* 
hamia titricularis , which is about 18 /x in length. The spindle in Spongospor a 
shows two clearly-defined poles with centrosomes, but the actual threads 
of the spindle in this division are not easy of differentiation, nor can the 
individuality of the chromosomes be made out. It is, of course, possible 
that there are no definite chromosomes in this division, the chromatin 
existing in a granular state, as Blackman has described in Coleosporium. 
The nuclear area often persists as a clear space during this first division 
(Fig. 2 8, a), though this is not so in all cases (Fig. 28,#). It is surprising 
how infrequently the ana- and telophases have been observed. A series 
of sections showing many plasmodia with their nuclei in the metaphase will 
show but few in the later stages of division, and this is true, moreover, for 
material of widely differing dates and hours of fixation. It is, perhaps, to 
be accounted for by a rapid movement of the chromatin masses towards 
the poles. Harper 1 found it otherwise in Fuligo varians , for, he says, c all 
stages in the separation of the daughter chromosomes and their migration 
to the poles of the spindle can be observed in the greatest abundance.’ All 
that can be said of the later stages of the first karyokinesis in Spongospora 
is that the chromatin splits into two apparently equal portions, which travel 
to the poles, retaining for some distance their plate-like character (Fig. 29). 
As they near the poles this appearance is lost, while the spindle fibres in 
the middle of the spindle disappear, though the apices and centrosomes are 
well marked (Fig. 30). The chromatin rounds itself off, while a new nuclear 
membrane appears. The second division is characterized by a shorter 
spindle (5 /x) and by the absence of any sign of the nuclear area at the meta- 
phase (Fig. 14). The later stages of this division resemble the preceding 
one, the chromosomes travelling to the poles in a mass (Figs. 33 and 34). 
In the plate stage, however, the spindle fibres can be differentiated with less 
difficulty, while sections transverse to the long axis of the spindle show 
a number of chromosomes — eight in those cases in which it has been 
possible to count them (Fig. 32). 
By the time that this division is completed the protoplasm has become 
rounded about each nucleus, so that there is a condition in which the 
organism consists of a number of uninucleate masses of protoplasm, the 
young spores, about which the spore wall then forms. The mature spores 
are spherical bodies about 4 /x in diameter, with a cell-wall, single nucleus, 
and a certain amount of oil (Fig. 35). The spore wall does not give 
a cellulose reaction with chlor-zinc iodine. 
The individual spore thus bears a strong resemblance to that of Plas- 
modiophora , as described by Nawaschin. The spores are loosely aggregated 
to form the structures referred to as c spore balls ’. These are of a shape 
varying from spherical to ovoid, while the diameter also varies, though 50 \ x 
1 Harper, R. A. : Bot. Gaz., vol. xxx, 1900, p. 233. 
