Survey of the Animal Kingdom Til 



and in cultures or infusions of decomposing materials. Hairlike cilia are present 

 at some stage in their life. 



Subclass A — Ciliata (sili-a'ta) (L. cilium, hairlike cilia). — Numerous 

 hairlike cilia are present in the adults for locomotion and for securing food. 

 A permanent mouth and gullet are usually present. 



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D 



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Fig. 77. — Life cycle of Monocystis, a gregarine protozoan of the class Sporozoa. 

 This is a common parasite in the seminal vesicle of the earthworm. A, Mature 

 individual (trophozote) attached to the seminal funnel of the earthworm; B, two 

 gametocytes, having formed a cyst around them; C, formation of gametes (sex 

 cells) ; D, conjugation of gametes to form a zygote; E, zygotes which have become 

 encysted spores; F, single spore whose original nucleus has divided into eight 

 nuclei; G, fully developed spore containing eight sporozoites; H, eight sporozoites 

 escaping from the sporocyst (spore case) into the intestine of a new earthworm 

 and eventually into its seminal vesicles; I, infestation of the sperm mother cells 

 of the seminal vesicle of the earthworm; spe, tails of withered sperms adhering 

 to the parasite; gam, gametes (sex cells) ; res, residual protoplasm; int, endocyst 

 (internal coat of the gamocyst) ; ext, epicyst (external coat of the gamocyst) ; 

 zy, zygote; spz, sporozoites; spc, sperm mother cells of the seminal vesicle. (From 

 Borradaile and Potts: The Invertebrata. By permission of The Macmillan Com- 

 pany and the Cambridge University Press, Publishers.) 



