H. B. Fantham 
385 
(Fig. 6, H). This method of reproduction, which is a form of 
schizogony, is comparable to the simple plasmotomy (Doflein) occurring 
in the Neosporidia. Up to the present this is the sole form of 
reproduction that has been described; the sporogony and mode of 
infection of the host are unknown. It is possible that resistant forms 
of Siedleckia exist, as Caullery and Mesnil state that they only 
obtained their material at a particular period of the year (August and 
September). Probably if the hosts were searched at their time of 
reproduction, the resistant phases of the parasite would be found. 
Fig. 6. Siedleckia nematoides, after Caullery and Mesnil (1899). 
A. Young trophozoite with two nuclei. 
B. Older form, with nuclei ( n) in a single row. 
C. D. Trophozoites still older, nuclei in single file. 
E. Full-grown parasite. Nuclei in a single row at the more pointed end, in two 
or more rows at the distal or rounded end. 
F. Parasite showing small multinucleate portions constricting off, by plasmotomy. 
G. Young, somewhat spheroidal form, produced by constricting off the parent, as 
in F. 
H. Older stage of a form, such as shown in G, which is now growing into a 
vermiform trophozoite. 
The systematic position of Siedleckia still remains undetermined. 
The general appearance and asexual multiplication by plasmotomy 
are certainly most suggestive of what has been described by Ldger 
(1900) for Schizocystis, while certain of Ldger’s sketches (see p. 383) 
of Schizocystis further support the view that there is probably some 
affinity between Siedleckia and Schizocystis. Caullery and Mesnil (1899), 
who described Siedleckia, noted its superficial resemblance to the 
