GREGARINIDA 63 



Class III. Sporozoa. 



Since the year 1879 a number of isolated uni-cellular parasites that 

 produce spores covered with shells are, according to R. Leuckart, included 

 with the gregarines, and this large group of protozoa is termed Sporozoa. 

 The Sporozoa comprise the so-called psorosperm tubes (J. Miiller), i.e., 

 Myxosporidia, Butschli ; the oval or round Psorospermia (Eimer), i.e., Coccidia, 

 Lkt., and Rainey's, or Miescher's tubes, i.e., Sarcosporidia, Biitschl. Later 

 the Microsporidia and the Hcsmosporidia were also classed with the Sporozoa. 



Order i. Gregarinida. 



Although hitherto the gregarinida have not been observed either in human 

 beings or .vertebrate animals, they must not be entirely omitted here, 

 because they belong to the oldest known sporozoa, and our knowledge of 

 them at the present time is less complete at any rate, in regard to the 

 history of development than that o-f other groups (Coccidia, H&mosporidia). 



Their bodies, which are usually elongated and frequently tape-like, and 

 the length of which varies according to the species between o - oi-i6 mm., 

 may consist of a single cell, as in the Monocystidea, inhabiting the body 

 cavity of echinodermata, annelida, &c., or may be divided into two or three 

 consecutive sections (Polycystidea, which invade the intestine, particularly of 

 arthropoda). 



FIG. 19. Monocystis a^ilis, St. From the vesicula 



seminalis of earthworms; 250/1 (After, v. Stein). 



(a) Quiescent ; (6) moving. 



The most anterior section, epimerit, is a variously-shaped % organ that is 

 used by the parasite to cling to the intestinal epithelial cells of its host ; 

 it is generally sunk within or between the cells, and when this condition 

 (cephalin, cephalont) is given up the epimerite is cast off, tricystic forms 

 thereby becoming dicystic. The next section, protomerit, is separated 

 from the principal section, the deutomerite, by an ectoplasmatic transverse 

 partition ; the large vesicular nucleus (figs. 20, 26), which is provided with a 

 usually round nucleolus (caryosoma). is situated in the deutomerit. 



The surface of the body is formed by a hyaline cuticle, which, however, 

 is not always so stiff as to prevent changes of form of the body. Beneath 

 the cuticle (fig. 21) there is a jelly-like mass that plays a part in the 



1 Butschli, O., " Sporozoa in Bronn's Cl. it. Ordn. d. Thierr., 1882, i., p. 479. Balbiani, 

 G., Lemons sur les sporoz., Paris, 1884. Wasielewski, " Sporozoenkunde," Jena, 1896. 

 Labbe, A., "Sporozoa," 5th Edition of " Thierreichs," Berl., 1899. Hagenmiiller, P., 

 " Bibliographic %in. et spec, des trav. cone. les. Sporoz." (Ann. Mus. hist. nat. Marseille, 

 1899, 2, i., Suppl.). Liihe, M., " Erqebn. d..neuer. Sporozoenforsch., Jena, 1900. 



