48 



PROTOZOA 



Order 1. MYXOSPORIDIIDA.- 



Sporozoan parasites which occur in various organs of fishes, insects, 

 and other animals; body amcrboid or sphwical and multinuclear ; sporu- 

 lation gives rise to sporoblasts in each of which one to several spores 

 develop: 4 families, including some dangerous parasites, one of which 

 is Glugea hombysis, the silk-worm parasite, which in thirteen years 

 previous to 1867 caused a loss in France of one billion francs. 



Family MYXOBOLIDAE. 



Parasites of fishes rarely found in the amoeboid form, but usually 

 as cysts filled with spores in which are vacuoles which are stained 

 reddish brown by iodine: 3 genera. 



Myxobolus Biitschli. Spores ovoid or elliptical: about 40 species. 



M. lintoni Gurley. In all the tissues of Cyprinodon variegatus. 



Order 2. SARCOSPORIDIIDA. 



Sporozoan parasites in the muscle fibres of 

 vertebrates; body elongate forming cysts with a 

 double membrane, in which are spores: 1 genus. 



2. Sarcocystis Lankester. Elongated Sporo- 

 zoa living in the muscle fibres of the pig, sheep, rat, 

 and other animals: about a dozen species. 



S. miescheriana (KiUm) (Fig. 71). Length of 

 cyst 3 ram. : in the pig. 



Class 4. INFUSORIA, t 



The Infusoria are distinguished by their defi- 

 nite body form, the outer surface of the body being 

 bounded by a firm cuticula, and by the possession 

 of cilia. These cilia are short hair-like pro- 

 jections of the ectosarc through the cuticula, 

 and in the various species may appear as rapidly 

 vibrating locomotory organs, or may be united 

 to form tentacles, spines, membranes, or suck- 

 ing tubes. The ectosarc is often highly specialized. 

 In many forms it contains large numbers of defensive organs 

 called trichocysts, which are minute rods lying perpendicular to 



* "The Myxosporidia or Psorospcmis of Fishes and the Epidemics Produced by 

 Them," by R. R. Gurley, Bull. U. S. Fish. Com., Vol. II, 1893. 



t See "A Manual of the Infusoria," by W. S. Kent, 1881. "A Preliminary Contri- 

 bution towards a History of the Fresh-water Infusoria of the United States," by 

 A. C. Stokes, Jour. Trenton Nat. Hist. Soc, Vol. 1, p. 71, 1888. 



Fig. 71 — Sarcocystis 

 m i e s c h e r i a n a 

 (Doflein). A, a cyst; 

 B, a piece of pork 

 containing cysts. 



