Capillitium in Certain Myxomycetes. 7 
form simultaneously along the thread rather than intermittently or pro- 
gressively. Even after the spirals have become quite distinct their edges 
can be seen on careful focusing to be made up of rows of granules. The 
material of the spiral certainly seems to be deposited as granules rather 
than as laminae. The walls of the young thread and the spirals when well 
enough developed to show characteristically their affinity for stains take up 
the orange in the triple stain, as do the young cell-walls in root-tips, pollen 
grains, &c. 
In Hemiarcyria clavata there are regularly four left-handed spirals 
on the capillitial thread (Fig. 5). Just why there should be this number 
and why the granular material should be distributed in spirals on the mem- 
branes of the thread is not obvious from any visible arrangement of the 
elements involved in their formation. Neither the position nor the arrange- 
ment of the nuclei or fibrillar rays suggests any explanation. 
The granular material in the interior of the capillitial thread (Figs. 1 
and q) becomes less as the wall thickens and the spirals appear, and as the 
thread matures it practically disappears (Figs. 3 and 4). There is, of 
course, no evidence that granular material as such passes from the interior 
of the thread into the forming spirals. We are inclined to suspect that the 
stainable granules in the interior of the thread are precipitation products 
formed in fixation, and that in the living condition the capillitial cavity 
contains only materials in solution in the cell-sap. These materials may be 
used up in the formation of the capillitial wall and spirals so that in late 
stages no such precipitation products are formed. 
At the stage shown in Fig. 5 the fibres have disappeared, the nuclei 
have lost their zonal distribution, and are scattered irregularly in the cyto- 
plasm as they were before the process of forming the capillitium began. 
The coarsely staining granules on which the fibrils were centred in the 
earlier stages have also disappeared, and it seems not improbable that their 
material has gone to the formation of the capillitial wall and the beginnings 
of the spiral thickening. At this stage the nuclei appear commonly to be 
of two types which are conspicuously differentiated from each other by their 
relative size and the density of their stainable constituents. The larger 
nuclei are similar in all respects in their appearance to the resting nuclei of 
earlier stages. The smaller nuclei are dense, show no nucleoles, and appear 
somewhat like daughter nuclei in early telophase stages (Fig. 5). These 
smaller nuclei are doubtless those which Kranzlin in 1907 ( 28 ) and Jahn in 
1907 ( 25 ) described as having failed to fuse, the larger nuclei corresponding 
to Jahn’s fusion nuclei. In view of his later observation of nuclear fusions 
in the first pairs of fusing swarm spores in the formation of the plasmodium, 
Jahn ( 27 ) has withdrawn his earlier interpretation of the presence of nuclei 
of two sizes at this stage in the development in the sporange. We have 
seen no division figures at just this stage. A little later, when cleavage is 
