THE NEOSPORIDIA 



417 



duced, which may form a conspicuous cyst. From the plasmodial stage 

 sporonts arise by separation of a mass of protoplasm round a nucleus within 

 the body of the parasite, and thus distinct cells are formed lying in vacuoles 

 in the plasmodium. Such cells are commonly termed " pansporoblasts," but 

 the use of this term is best avoided, since the cells La question are in no 

 way equivalent to the pansporoblasts of Myxosporidia, which are associa- 

 tions of two gamonts ; but they correspond exactly to the sporonts of 

 Nosema and other genera, and proceed to the formation of spores in the 

 manner that has been described already, dividing first into several 

 sporoblasts. 



The plasmodia of the Olugea-typo lead, as already stated, to the forma- 

 tion of conspicuous cysts, visible to the naked eye, in the tissues of the 

 host ; but the composition and nature of these cysts are at present a matter 

 of dispute. According to Stempell (784), in Qlugea anomala, the body of the 

 parasite is sharply defined and marked off from the tissues of the host by a 

 thick membrane or autocyst (" Eigencyst ") formed by the parasite itself 

 (Fig. 174, e). Within the autocyst is contained the plasmodium, consisting of 







FIG. 174. Qlugea anomala, Honiez : part of a section of a cyst, e., Envelope 

 (autocyst) ; bn, vegetative nuclei ; sp., spores ; pap, sporont lying in a space 

 in the protoplasm. After Stempell. 



protoplasm containing many nuclei, amongst which the most conspicuous 

 are large indeed, relatively gigantic vegetative nuclei, which multiply by 

 direct division. From the vegetative nuclei the minute nuclei of the sporonts 

 are stated to arise, while in other case vegetative nuclei break up and de- 

 generate. 



Schroder (781) and Schuberg, on the other hand, maintain that the large 

 vegetative nuclei of Stempell are in reality tissue-nuclei of the host, greatly 

 hypertrophied and mixed up with the plasmodium of the parasite. Schuberg 

 found that Pleistophora longifilis, from the testis of the barbel, causes a hyper- 

 trophy, not only of the host-cell in which it is contained, but also of neigh- 

 bouring cells, the effect of which is to produce a sort of host-plasmodium, as 

 it were, containing gigantic host-nuclei of irregular form (Fig. 171), amongst 

 which the sporonts and spores of the parasite are scattered. Mrazek also 

 interprets the supposed vegetative nuclei of Myxocystis as hypertrophied 

 host-nuclei (see below). This interpretation of the composition of the plas- 

 modium greatly diminishes, or even abolishes, the principal distinction between 

 Qlugea and the other genera of Microsporidia. In opposition to this view, 



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