380 



GENERAL ZOOLOGY 



forms a number of sporozoites. The oocyst bursts, liberating 

 the sporozoites in the body cavity, whence they find their way 

 via the body fluids to the salivary glands (Fig. 212). 



Tertian malaria is so called because the chill comes at the 

 end of 48 hours, i.e., on the third day. Other forms of malaria 

 have a different incubation period and are caused in each case 

 by a different species of parasite. The life 

 histories are all similar to that of P. vivax 

 given above, though differing in details. 

 SUBCLASS 2. CNIDOSPORIDIA. Amoe- 

 boid multinucleated forms, undergoing 

 continuous spore formation. Spores charac- 

 terized by thread capsules. 



Example: Myxobolus lintoni, occurring in 

 the subcutaneous tissue of the carp. 

 SUBCLASS 3. ACNIDOSPORIDIA. Para- 

 sitic in invertebrates and vertebrates. 

 Reproduction continued through vegetative 

 life. 



Example: Sarcocystis miescheriana, para- 

 sitic in the muscles of the pig (Fig. 213). 

 SUBPHYLUM 2. CILIOPHORA. Protozoa 



PROVIDED WITH CILIA THROUGHOUT LIFE OR 



IN early stages. Cilia are short processes 

 resembling hairs, located on the surface of the 

 body (Fig. 2, B). 

 CLASS I. CILIATA. Ciliated protozoans 

 with a firm pellicle. A macronucleus and one 

 or more micronuclei are present, except in 

 parasitic species. A mouth (cytostome) and 

 gullet (cytopharynx) are usually present, 

 along with food vacuoles and contractile vacuoles. The ecto- 

 plasm or ectosarc may contain trichocysts, which are small sacs 

 containing poisonous fluid that is discharged, with the sacs, for 

 purposes of offense or defense. In the water the trichocysts 

 are converted into long, thin threads. The cytoplasm may 

 also contain contractile fibers called myonemes. Cirri and 

 membranelles may be present. A cirrus is formed by the fusion 

 of a small tuft of cilia; a membranelle by the fusion of two or 

 more transverse rows of cilia. Cirri are used in creeping over 



Fig. 213. — Sarco- 

 cystis miescheriana, 

 from the pig's dia- 

 phragm. The or- 

 ganism, enclosed in 

 a cyst, has divided 

 into numerous al- 

 veoli, each contain- 

 ing a number of 

 spores some of which 

 are shown free where 

 the cyst has been 

 cut open. (After 

 Mam.) 



