33 2 Osborn. — Spongospora subterranea , ( Wallroth ) Johnson . 
seen rods and granules of deeply staining chromatin surrounded by a non- 
staining area. These gradually become more marked until in the new 
nucleus there maybe seen a considerable mass of chromatin in a lump, often 
lying to one side of the membrane (PL XXVII, Fig. 21), while at the same 
time the protoplasm appears less granular. 
The most satisfactory explanation of these facts would appear to be that 
on the reconstruction of the nuclei the chromidia are reduced in number, 
though they do not totally disappear, and thus there is a certain wastage of 
chromatin, which ultimately degenerates. The chromatin mass in the new 
nucleus gradually becomes less contracted, and a network arrangement is to 
be seen (Fig. 22), though there is no sign of a karyosome or nucleolus. 
Bloomfield and Schwartz, when describing a similar stage in Sorosphaera 
Veronicae , were unable to state where the fresh nuclei appeared in relation 
to the old ones, but in X. Junci Schwartz says he observed ‘granules and 
irregular masses of chromatin forming fresh nuclei in the vacuoles \ 1 
Karyogamy and spore formation. The reproductive nuclei are to be 
seen at first irregularly scattered through the whole plasmodium. It is soon 
to be noticed, however, that there is a very definite association in pairs 
(Figs. 9 and 10). This in itself is suggestive of a fusion, and all stages of 
the occurrence have been observed in numerous plasmodia (Fig. 11). In 
a pair of fusing nuclei, the membrane at the point of contact breaks down, 
and their contents merge one into the other (Fig. 23). The union occurs at 
approximately the same time for all pairs of nuclei in a plasmodium, so that 
the various stages are by no means rarely to be seen (Fig. 24). Such nuclei 
as are unable to pair degenerate and are quickly lost to sight. 
The fusion nucleus has an appreciably increased diameter (5 //), while 
its chromatin matter appears in the form of threads (Fig. 25). It is at this 
period that there is the greatest difficulty in arranging the various stages in 
their proper sequence. The plasmodia are so small that no progressive 
series of changes can be seen in the single plasmodium, as has been recorded 
for various Mycetozoa, but careful comparative study of different plasmodia 
of Spongospora leads to the following account. The chromatin matter con- 
tracts to form a dense irregular mass lying within the enlarged membrane. 
The appearance at this stage is strongly suggestive of a synapsis (Fig. 26). 
On emerging from this state the chromatin is in the form of granular threads 
(Fig. 27) arranged along a diameter of the cell (Fig. 12), but unfortunately 
I cannot state with certainty the various stages that must intervene between 
this condition and the first karyokinesis, nor am I able to say, from my own 
observations, whether a condition of diakinesis occurs or not. 
The first karyokinetic division is marked by a well-defined but very 
dense plate of chromatin lying equatorially on a spindle which is relatively 
long compared with the diameter of the plate (Fig. 13). The spindle, how- 
1 Schwartz, E. J. : loc. cit., p. 516. 
