PHYLUM PROTOZOA 



83 



to the protomerite there is sometimes found, especially in young 

 individuals, a third division, the epimerite {ep.), which may be 

 provided with hooks (B^), serving to attach the parasite to the 

 epithelium of the intestine of its host, by becoming embedded in 

 the substance of one of the cells. As maturity is reached the 

 epimerite is thrown off (B^), and the parasite then lies freely in the 

 cavity of the intestine. 



The cysts of Gregarina (C) are often very complex and 

 provided with delicate ducts {spd.) in the thickness of the wall, 



Fig. 63.— ^Gregarina. Development from the sporozuite. i, cells of the digestive epithelium 

 of the host ; 3, nuclei of the same ; 5, spore ; It, spore discharging sporozoites (5) leaving 

 residual mass (S) ; '7, sporozoites in the act of entering epithelial cells; S, the same as 

 intracellular parasites ; 9-12, different stages in the growth of the young Gregarines into the 

 lumen of the intestine ; i5, epimerite ; lU. protomerite; 15, dcutomcrite. (After Lang.) 



through which the spores escape. In Gregarina gigantea of the 

 Lobster, ^he young (sporo^oife) is liberated from the spore in the 

 form of a non-nucleated amoebula (D^), with one long and one 

 short pseudopod (D^) ; this divides by the long pseudopod {fsd. 2) 

 becoming separated off, and each product of fission, developing a 

 nucleus, passes into the adult (trophozoite) form (D^, D*.) In 

 other species of Gregarina the sporozoites do not divide, but each 

 develops directly into the trophozoite (Fig. 63). 



Order 2. — Coccidiidea. 



Coccidium (Figs. 64, 65) and allied genera are parasites in the interior of 

 cells, both in Vertebrates and Invertebrates. They live in the cells of various 



G 2 



