INIJ'USORIA. 29 



Malaria. 



The malarial fevers, our old Fen ague, are produced by 

 species of Plasmodium (Marchiafara and Celli) ; other species 

 also occur in mammals and birds. In all cases the agents of 

 transmission are mosquitoes or Culicidse ; in the human malaria 

 only Anopheline Culicidae can carry the parasites. There are 

 three species (1) of Tertian fever (P. oivax), (2) the quartan 

 parasite {P. malari(K), and (3) the pernicious or tropical s])eoies 

 (P. wimaculaium). One marked character of these is that they 

 produce a black substance called Melanin. The parasites are 

 injected into man's blood by the Anopheline mosquito, and 

 then enter the red corpuscles, feed, grow, break up into spores, 

 and destroy the corpuscles ; the spores enter other blood cor- 

 puscles, and so the fever is set up. The Anopheline, whilst 

 taking man's blood, injects the parasites with the saliva, and 

 the insect at the same time obtains other forms from the blood, 

 and a male and female stage is formed in the insect. The male 

 throws off portions which conjugate with or fertilise the female 

 parasite, which then wanders into the walls of tlie stomach and 

 later, on the outer wall, grows to a great size and eventually 

 breaks up into a large number of elongated spores, which enter 

 the salivary glands of the mosquito. In man, therefore, we get 

 asexual spore -formation (schizogony), in the mosquito sexual 

 generation ending in sporogony. 



CLASS IV. INFUSORIA. 



The Infusoria are Protozoa which are provided with cilia for 

 locomotory purposes. They have also a vegetative macro- 

 nucleus and a generative micronucleus. 



At one time the Flagellata were included in this class. 



There are two sub-classes — (1) Giliata and (2) Sucforia. 



In the first the cilia occur during the whole active life of the 



