E. N. Pavlovsky and N. N. Anitchkov 
311 
The above comparison shows that our species differs from the previously 
known three species by the following features: (1) the position of the ventral 
sucker which is anterior to the middle of the body; (2) the position of the cyst- 
glands in the anterior third of the body and (3) the occurrence of the parasite 
in Schizothorax intermedins, an indigenous fish. These characters form a 
sufficient basis to create for the above described larva a new species which 
we have named Tetracotyle sogdiana. 
Peritoneum as a Site of Localisation of the Parasite. 
The occurrence of Tetracotyle cysts under the peritoneum of Schizothorax 
is by no means exceptional. In fact, in the 17th Book of Susswasserfauna 
Deutschlands by Liihe, in addition to the species of Tetracotyle, the following 
other Trematodes are mentioned occupying a similar position in their hosts: 
(1) Monostomum sp. occurring on the surface of the pyloric appendages of 
Coitus gobio and on the stomach of Coregonus albula. (2) Cysts of embryo 
Distomum found under the peritoneum of Acerina ceruna and Perea fluviatilis. 
(3) A Distomatid found in a similar condition in Cottus gobio and Nemachilus 
barbatula is regarded as a doubtful form. 
Amongst other parasitic worms the following were frequently found under 
the peritoneum of their hosts: 
The larvae of Bothriocephalus sp. in Coregonus maraena, C. albula, Sahno 
solar ; cysts of larvae of Triaenophorus nodulosus in Coregonus lavaretus, 
Salmo trutta, S.fario, S. hucho, S. salvelinus; cysts of Bothriocephalus osmeri 
in Osmerus eperlanus; larvae of Pomphorhynchus laevis (?) in Osmerus eperlanus 
and Salmo fario; cysts of larvae of Tetrarhynchus paleaceus in Salmo salary 
cysts of larvae of Diplostomum cobitidis in Nemachilus barbatula. 
Among all the above mentioned parasitic worms, our species is of special 
interest as it represents the only case where the pathologico-anatomical 
changes of the host have been investigated in detail. 
Structure of the Cyst-walls. 
We have mentioned above that the cysts containing the parasites are en¬ 
closed within a special patchlike thickening of the peritoneum which is attached 
to the ventral side of the visceral bundle and is connected with the abdominal 
wall by means of fine adhesive fibres. The sections through the entire patch and 
through the adjacent portions of viscera show that the cysts (Fig. 7,c.) are sur¬ 
rounded by a connective tissue membrane produced by the inflammatory re¬ 
action of the tissue. In some areas these cysts, surrounded by the connective 
tissue capsule, appear to wedge in between the lobules of the pancreatic glands 
many of which are seen to be compressed and atrophied or in a state of partial 
necrosis. 
The capsule surrounding the parasite consists of several layers characterized 
as follows: 
(1) The layer nearest to the parasite (Fig. 8, a.) appears in transverse section 
