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differentiated cell as is the polar capsule of Cnidosporidia, it differs from the 
latter in several essential characters. 
The following table shows the points of difference between these two 
structures: 
Spiral filament of Helicosporidium 
(1) Filament not enclosed in a polar capsule 
but lies free beneath the wall of spore. 
(2) Filament always unrolls in the dead body 
of its host. 
(3) Filament unrolls slowly. 
(4) Filament pointed at both ends and wide 
and ribbon-like in the middle. 
(5) Axial portion of filament is very chro¬ 
matic, nucleus well formed in anterior 
third of filament. 
(6) Filament robust, very resistant in all 
media. 
Polar-capsule filament of Cnidosporidia 
(1) Filament enclosed in a capsule of which it 
forms a part. 
(2) Filament does not unroll until spores 
reach intestine of a second host. 
(3) Filament is shot out. 
(4) Filament pointed at one end only and very 
fine. 
(5) No chromatic axial portion, degenerated 
nucleus upon wall of terminal capsule. 
(6) Filament fine and very fragile. 
The foregoing shows clearly that the spiral filament of Helicosporidium is 
of a nature totally different from that of the polar capsule of the Cnidosporidia. 
Other distinctive characters of Helicosporidium are: (1) the wall of the spore 
does not seem to be formed by a specialised cell, at any rate no trace of such 
a cell could be detected in the wall of the completely formed sporocyst; 
(2) the spore of Helicosporidium does not show T a binary or ternary symmetry 
and pansporocysts are non-existent. 
All this demonstrates clearly enough that there is no real affinity between 
the genus Helicosporidium and the Cnidosporidia. 
2. Helicosporidium and Haplosporidia. 
We may now compare the genus Helicosporidium with the Order Haplo¬ 
sporidia of Caullery and Mesnil (1905). Although this Order, conceived in its 
widest sense, is heterogeneous, all the forms which it comprises differ greatly 
from Helicosporidium. In their life-cycle they have a plasmodium stage and 
a cyst which surrounds the spores; these characters never appear in the life- 
historv of Helicosporidium. The spores of the Haplosporidia are unicellular 
with one or two envelopes while the spores of Helicosporidium are composed 
of four cells of different structure. These differences are sufficient to show that 
there is no affinity between Helicosporidium and the Haplosporidia. 
3. Helicosporidium and Serumsporidia. 
It remains finally to be seen whether or not there are some relations 
between Helicosporidium and a few Protists temporarily placed in the Sporozoa 
but whose systematic position is still subjudice. The only group anions these 
Sporozoa which may interest us is the group of Serumsporidia of Pfeiffer. 
Under the generic name of Serumsporidium., Pfeiffer (1895) has described 
a certain number of parasites which he discovered infesting the body cavity 
