796 THE GREGARINIDA 



barrel-shaped structure. These crescent-shaped merozoites then escape from 

 the cell host and become sporozoites which pass into the body cavity of the 

 animal. 



Among the best known Gregarines are Porospora gigantea (parasitic in the intes- 

 tine of Astacus gammarus) ; Gregarina blattarum (parasitic in the intestine of Blatta 

 orientalis) ; Monocystis tenax (a parasite of the earthworm) ; Lankesteria ascidice 

 (a parasite of Ciona intestinalis). 



Technique. For the examination of the Gregarinida, Wasielewski recom- 

 mends osmic acid or a saturated solution of perchloride of mercury as a fixing 

 agent, and safranin, picro-carmine, gold chloride or silver nitrate as a stain. 

 Bertarelli advises fixing in acid perchloride or in Flemming's solution and 

 staining in iron-hsematoxylin or Delafi eld's haeinatoxylin. 



