84 



ZOOLOGY 



SECT. 



ORDER 3. H^MOSPORIDIA. 



Sporozoa in which the trophozoite is amoeboid, and lives as 

 a parasite in the coloured blood-corpuscles of Vertebrates. 



ORDER 4. MYXOSPORIDEA. 



Sporozoa in which the trophozoite is amoeboid, but not intra- 

 cellular. 



ORDER 5. SARCOCYSTIDEA. 

 Elongated Sporozoa, usually found in muscle. 



Systematic Position of the Example. 



Monocystis agilis is a species of the genus Monocystis, belonging 

 to the family Monocystidce, of the order Gregarinida. It is placed 

 in the Gregarinida on account of being free and motile in the tro- 

 phozoite state. The absence of partitions dividing the protoplasm 



B 



FIQ. 63. Oregarina. A, two specimens of G. blattarum partly embedded in enteric 

 epithelial cells of Cockroach ; J5 1 , J5 2 , two specimens of G. dujardini ; in B z the epimerite 

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

 Z), four stages in the development of G. gigantea. cy.cyst; deu. deutomerite ; ep. epimerite ; 

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

 psd. 2, long pseudopod ; sp. mass of spores ; spd. sporoducts. (From Biitschli's Protozoa.) 



into segments indicates its position among the Monocystidse. 

 Monocystis is distinguished by its elongated form, by the absence 

 of any special apparatus in the cyst for the liberation and dispersal 

 of the spores, and by its spindle-shaped spores with thickened 

 ends, each producing 4-8 falciform young. The differences 

 between the species of Monocystis depend largely upon size. 



ORDER 1. GREGARINIDA. 



Monocystis is one of the simpler representatives of the Gregarinida 

 as regards both structure and life-history. The structure of the 

 adult or trophozoite is complicated in Gregarina (Figs. 63 and 64) 



