384 
The Scliizogregarines 
claviform and uninucleate, grow without change of form into gameto- 
cytes. The gametocytes associate in pairs, encyst, and form isogamous 
gametes, which conjugate in pairs and give rise to many sporocysts, 
laconical in shape and peripherally arranged inside the gametocyst. 
The spore-formation therefore takes place on the plan generally pre¬ 
vailing among the Gregarines. 
(4) Genus Siedleckia. 
The genus Siedleckia Caullery and Mesnil (1898) was created for 
Siedleckia nematoides, a somewhat aberrant parasite inhabiting the di¬ 
gestive tract of the Polychaetes, Scoloplos muelleri and Aricia latreillei 1 . 
The discoverers have noted its resemblance to vermiform Schizogre- 
garines like Selenidium. It is also very like Schizocystis in appearance, 
for it is nematoid in shape, and it is multinucleate. It has a similar 
habitat to Selenidium, and performs similar movements. The parasite, 
as stated, is a small vermicular organism, of which one extremity is fixed 
to the wall of the gut and is immobile, while the other or distal 
extremity is free, and executes vigorous helicoid movements of torsion 
and flexion. 
The size of Siedleckia varies, specimens ranging in length from 
8/4 to 150/4. While they are very transparent, their protoplasm is 
granular. In life, clear ai’eas are seen at intervals. These are the 
nuclei, which appear to greater advantage in stained preparations. 
The young forms are somewhat spindle-shaped and have few nuclei 
(Fig. 6, A); as they increase in size nuclear multiplication occurs 
(Fig. 6, B, C). The nuclei at first lie one behind the other in a single 
row (Fig. 6, B, C, D), but as they increase in numbers the order is 
broken and several rows may be seen (Fig. 6, E). This nuclear increase 
is far more noticeable in the distal or free end, which is rounded, than 
in the proximal portion (Fig. 6, E), which may be attached to the cells 
of the host. When the number of nuclei reaches about 120, asexual 
reproduction commences. 
The parasite is now about 150/4 long, and contains a relatively 
large number of nuclei. Its growth still continues, but at the same 
time protoplasm collects around certain peripheral nuclei at the distal 
end, and these become successively constricted off (Fig. 6, F) as small, 
spherical masses, each with a very small number of nuclei (Fig. 6, G). 
Each of these buds probably can develop into a new Siedleckia 
1 Dobell (Q. J. M. S., Jan. 1909) found Siedleckia in Aricia fcetida. 
