76 ZOOLOGY SECT. 



markedly from the naked spores of the Rhizopoda and Mastigo- 

 phora. The protoplasm of each spore then undergoes fission, 

 becoming divided into a number of somewhat sickle-shaped 

 bodies, which are arranged within the spore-coat somewhat like 

 a bundle of sausages. By the rupture of the spore-coat these 

 falciform young are liberated and at once begin active move- 

 ments, the thin end of the body moving to and fro like a clumsy 

 flagellum. The falciform young appear, in fact, to be greatly 

 modified flagellulse. They make their way to the clumps of 

 developing sperms, bore their way in, and are thus found sur- 

 rounded by sperm-cells in various stages of development (D F). 

 After thus living an intra-cellular life for a time, they escape into 

 the cavity of the vesicula (G) and grow into the adult form. 



2. CLASSIFICATION AND GENERAL ORGANISATION. 



The Sporozoa are exclusively parasitic, being the only group of 

 Protozoa of which this can be said. They have no organs of 

 locomotion and always multiply by spore-formation. The class is 

 divisible into the following four orders : 



ORDER 1. GREGARINIDA. 

 Sporozoa in which the adult is free and motile. 



ORDER 2. COCCIDIIDEA. 

 Sporozoa in which the adult is a minute intra-cellular parasite. 



ORDER 3. MYXOSPORIDEA. 



Sporozoa in which the adult is amoeboid. 



ORDER 4. 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 

 adult state. The absence of partitions dividing the protoplasm 

 into segments indicates its position among the Monocystidse. 

 Monocystis is distinguished by its elongated form, by the absence 

 of any special apparatus in the C}*st 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. 



