PROTOZOA. 



17 



3. GREGARINA. 



Gregarines are Protozoa, often of worm-like form, in which a 

 relatively large size may be attained (up to f of an inch long). 

 They are parasitic, living at the expense of other animals, and as 

 they are found within the bodies of these " hosts," may be termed 

 endoparasites. Since they are surrounded by abundance of nutri- 

 tious food, there is no necessity for locomotor or current-producing 

 organs, and, in fact, there are neither pseudopodia nor cilia, and 

 digestive organs are absent as well. 



Fig. 3. GREGARINES (after Stein and Biitschli). Enlarged to various 

 scales. A-E, Stages in the life-history of Monocystis off His; A, adult ; 

 co, cortical layer (dotted) ; n, nucleus ; B, cyst, with developing 

 spores ; C, cyst, with ripe spores ; D, a spore with contained falciform 

 young ; E, one of the falciform young ; F-K, stages in the life-history 

 of Gregarina blattarum ; F, young adult ; ep, epitnerite ; pr, proto- 

 merite ; deu, deutomerite containing nucleus, n ; G, cyst containing 

 two conjugated individuals; H, ripe cyst; g.l, gelatinous layer; 

 f.l, firm stratified layer, within which is a network, still enclosing 

 spores in the centre ; sp, sporoduct ; K, a spore ; L, epithelial cells 

 from intestine of cockroach, with attached stages (1, 2, 3) of developing 

 spore-contents. 



The vesiculse seminales of the earthworm are infested with one 



kind of Gregarine, to which the name of Monocystis has been 



applied. This has a cylindrical body (Fig. 3), which in the 



largest species may be -J- of an inch long. It is covered with a 



2 2 



