326 Sporozoa 



Therefore, the striated membrane may be a product of the host rather 

 than of the parasite. 



The term, "spore," is applied rather loosely to the elongated stages 

 which develop in the sarcocyst, since there is no apparent spore mem- 

 brane. The visible structures include a nucleus and more or less promi- 

 nent granules (Fig. 6. 34, A-D). Several workers have noted that these 

 "spores" can undergo twisting movements, rotation on the long axis, 

 longitudinal contraction and elongation, or even locomotion (120). 



Although the Sarcosporidia are commonly considered Protozoa and 

 placed in the Acnidosporidea for lack of a more appropriate place, their 

 protozoan nature has been questioned. One suggestion is that Sarcocystis 

 from hogs is a fungus, identified as a species of Aspergillus. The re- 

 ported evidence involves: (1) recovery of such a mold from cultures 

 inoculated with sarcocysts removed from muscles of hogs; (2) recovery of 

 sarcocysts from muscles of young pigs inoculated with conidia from such 

 cultures; (3) recovery of a similar mold from experimentally infected 

 animals (124). If this report can be confirmed, it should be possible to 

 transfer to the mycologists the puzzling problems involved in taxonomy 

 of the Sarcoporidia. 



Aside from their interest as unusual parasites of uncertain relation- 

 ships, the Sarcosporidia are of some importance in veterinary medicine 

 as parasites of cattle, horses, sheep, and hogs. Sarcoporidiosis of man is 

 apparently rare, although cases are reported occasionally (33). 



Subclass 2. Haplosporidia 



These organisms show certain similarities to the Cnidosporidea, 

 although they produce cysts without polar filaments. Species have been 

 reported from fishes, tunicates, insects, molluscs, annelids, nemertines, 

 trematodes, and rotifers. They have been found in the coelom or other 

 body cavities and also in tissues and individual cells in different cases. 



The life-cycles are incompletely known. In some species, a small amoe- 

 boid stage emerges after a spore is ingested by the host. This uninucleate 

 or binucleate trophozoite (Fig. 6. 35, A) may invade a tissue cell or some 

 tissue of the host, or else make its way into a body cavity, where develop- 

 ment is continued. Growth is usually accompanied by nuclear divisions 

 (Fig. 6. 35, B), and the plasmodia of certain species contain many nuclei 

 (Fig. 6. 35, C). In Coelosporidium periplanetae, however, occasional fis- 

 sion of binucleate trophozoites occurs, in addition to the development of 

 Plasmodia (60). Division of plasmodia into uninucleate stages (Fig. 6. 35, 

 D, E) also occurs in Coelosporidium (60) but has not been reported in 

 Haplosporidium (63). 



The development of spores resembles that in certain Microsporidia. 

 Uninucleate sporoblasts are formed within a mature plasmodium and 

 each sporoblast apparently develops directly into a spore (Fig. 6. 35, F-H). 



