PHYLUM PROTOZOA 



77 



ORDER 1. GREGARINIDA. 



All the more typical members of the class belong to this 

 group. With the exception of Monocystis, already described, the 

 only genus to which it will be necessary to draw attention is 

 Grcgarina (Fig. 56), the various species of which are parasitic in 

 the intestines of Crayfishes, Cockroaches, Centipedes, and other 

 articulated animals. It differs from Monocystis in having the 

 medullary protoplasm of the adult divided into two sections, an 

 anterior, the protomerite (pr.\ and a posterior, the deutomerite 

 (deu.), in which the nucleus is situated. Anteriorly to the proto- 

 merite there is sometimes found, especially in young individuals, 



D 4 



FIG. 56. Gregrarina. A, two specimens of G. blattarum partly embedded in enteric 

 epithelial cells of Cockroach ; Bi, B2, two specimens of G. dujardini ; in B2 the epimerite (<;*.) 

 is cast off ; C, cyst of G. blattarum, from which most of the spores have been discharged ; 

 D, four stages in the development of G. gigantea ; cy. cyst ; deu. deutomerite ; cp. epimerite ; 

 p. gelatinous investment of cyst ; nu. nucleus ; pr. protomerite ; psd. 1, short pseudopod ; 

 ; /*.w. 2, long pseudopod ; sp. mass of spores ; si>d. sporoducts. (From Biitschli's Protozoa.) 



a third division, the epimerite (cp.), which is sometimes provided 

 with hooks (B 1 ), serving to attach the parasite to the epithelium 

 of the intestine of its host. As maturity is reached the epimerite 

 is thrown off (B 2 ), and the parasite then lies freely in the cavity of 

 the intestine. 



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

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

 through which the spores escape. In Gregarina gigantea of the 

 Lobster, the young is liberated from the spore in the form of a non- 

 nucleated amcebula (D 1 ), with one long and one short pseudopod 

 (D 2 ) ; this divides by the long pseudopod (psd. 2) becoming sepa- 

 rated off, and each product of fission, developing a nucleus, passes 

 into the adult form (D 3 , D 4 .) 



