346 
Pleistophom gigantea, Thelohan 
(2) Oligosporogenea, the trophozoite produces only one pansporo¬ 
blast containing four (Gurleya), eight (Thelohania), or many (Pleisto- 
phora) spores. 
The parasite which I am about to describe has been found in a 
cutaneous tumour and in the mesenterium of Crenilabrus melops. 
Thelohan (1895) describes a parasite {Glugea gigantea) in the peritoneal 
cavity of the same fish; he does not mention any stages of the life- 
cycle, but only states that a polar filament was not to be found within 
the spores. It is difficult to ascertain the identity of Thelohan’s parasite 
and mine, but this identity is probable considering the absence of a 
polar capsule in the spores of both parasites and the identity of the host. 
My parasite, however, is no Glugea, the trophozoite being directly 
transformed into a pansporoblast; consequently it is a Pleistophora 
and its name should be Pleistoplioi'a gigantea. 
2. Material and Methods. 
The different stages of the life-cycle of P. gigantea were found in a 
large tumour, situated on the ventral side of the head and the thorax of 
Grenilahrus melops (PI. XVII, fig. 1), reaching from the posterior margin 
of the gills to the ventral fins. The tumour was caused by hypertrophy 
of the subcutaiieous tissue; it did not show any sign of infiltrative 
growth: the gills and the organs of mouth and thorax were left quite 
unaffected. The tumour was so heavy as to deprive the fish of its 
hydrostatic equilibrium {vide Pi. XVII, fig. 1, representing the living fish). 
Portions of the tumour were fixed in corrosive alcohol (after 
Schaudinn’s prescription), washed in alcohol and iodine, hardened in 
absolute alcohol, mounted in paraffine, and cut into sections of 3-5 g. 
The stains employed were hematoxylin (Ehrlich’s, Delafield’s, or 
Heidenhain’s) or Giemsa’s solution. 
To demonstrate the polar filaments, living spores were treated with 
caustic soda or potash ; sulphuric-, nitric-, and hydrochloric-acid, methyl 
alcohol, ether, iodine, and distilled water, but no filament was to be 
seen. 
3. Description of the Life-historg of P. gigantea. 
The tumour already mentioned is composed of connective tissue and 
multinucleate giant cells. In this tissue are embedded cysts of different 
size containing spores and sporoblasts (PI. XVIII, fig. 3). At times a 
large cyst is surrounded by a series of small cysts, suggesting that the 
