II 



PHYLUM PROTOZOA 



77 



ORDER 1. GREGARIXIDA. 



All the more typical members of the class In-long to thi- 

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

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

 Gregarina (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 protomcritc (pr.), and a posterior, the deutomerite 

 (dcu.\ in which the nucleus is situated. Anteriorly to tli- proto- 

 merite there is sometimes found, especially in young indi\ iduals, 



dou. 



spd 



FIG. 56. Gregrarina. A, two specimens of C-t. liintturiini partly eiiiK-<M<;>l in 

 epithelial cells of Cockroach ; B 1 , B 2 , two specimens of ft. dujardini ; in 1.5- tin epii 

 is cast off ; C, cyst of G. llattarum, from which must of the spores have li.vn discharged : 

 D, four stages iii the development of G. r/;</<i,>/,<i : cy. cyst ; deu. deutomerite ; p. epimerite ; 

 (/. gelatinous investment of cyst; nu. nucleus ; jn: protomerite ; px,i. 1, sluu-t pM-u.l'>]M><l ; 

 ps<L 2, long pseudopod ; j). mass of spores ; spd. sporoducts. (From Biitschli's l',-ot<>:.i><i. ) 



a third division, the epimeritc {e^>.}, 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 : ), 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 Grc<jrintt gigantea of the 

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

 nucleated amcebula (D 1 ), with one l..ng and one short p>nido|.od 

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

 rated off, and each product of fission, developing a nucleus, passi - 

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



