MORPHOLOGY AND CLASSIFICATION l6l 



with eight flagella and is hollowed out at one side near the rounded 

 anterior end to form a suction cavity. 



Rhizopods. — The members of the second class, Rhizopoda, 

 are characterized by their ability to send out protoplasmic proc- 

 esses to serve for locomotion and also to surround and engulf 

 solid food particles. The two genera, Amoeba and Endamceha, 

 are of chiefest interest. The organisms are masses of protoplasm 

 containing a nucleus, food granules and sometimes vacuoles, and 

 surrounded by a slightly denser more hyaline layer of ectoplasm. 

 The members of the genus Amosba are free-living saprophytic 

 forms, while those of Endamceba are parasitic. Multiplication 

 occurs by fission after a more or less complex division of the 

 nucleus. Multiple division also occurs, more especially in an 

 encysted condition, and • subsequent to a possible autogamic 

 fertilization. 



Sporozoa. — The third class, Sporozoa, is made up entirely 

 of parasitic forms, which at some stage in their life history multiply 

 by division into numerous daughter cells, which are enclosed in a 

 protective envelope to form a spore. The spores serve to dis- 

 tribute the species to other hosts. In cases where there are special 

 adaptations for distribution, as for example by means of inter- 

 mediate hosts, the protective envelope may be absent. An enor- 

 mous number of parasitic micro-organisms are included in this 

 group. The genera of greatest present interest from the patho- 

 logical point of view are Eimeria (Coccidium), Plasmodium, 

 Babesia (Firoplasma) and Nosema. 



The Coccidia. — ^£mma . includes a number of intracellular 

 parasitic forms, perhaps better known as coccidia. The small 

 parasite resulting from asexual division is called a merozoit. It 

 is somewhat spindle-shaped and 5 to lo/i long. This merozoit 

 penetrates an epithelial cell of the host, grows at the expense of 

 the cell to a spTierical mass 20 to 50^ in diameter, and eventually 

 divides into numerous (sometimes as many as 200) merozoits, 

 which become free by rupture.of the host cell. Besides this asex- 

 ual mode of multiplication, there is also a sexual cycle. Some of 

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