4 BRANCH PROTOZOA 



It is said that in the bodies of some Radiolaria are found unicellular 

 Algse, or microscopic plants, which furnish, even in this low stage of life, 

 an example of symbiosis, or the living together of different kinds of organisms 

 for mutual benefit. 



CLASS II. MASTIGOPHORA 



The Eugle'na is a representative of the second class of Pro- 

 tozoans (Mastigoph'ora). It has a more fixed arrangement 

 of parts than the Amceba. The cell is surrounded by a delicate 

 membrane perforated at the blunt anterior end by a funnel- 

 shaped mouth through which the food passes into the body sub- 

 stance. From the base of this mouth the protoplasm extends 

 out in a long flagellum which, by its lashing, propels the body 

 forward, and produces currents of water which bear food into 

 the mouth. Back of the mouth is a tiny pigment spot beside a 

 clear space which is sensitive to light. 



CLASS III. SPOROZOA 



This class consists of parasitic protozoans. The Gregari'na 

 is parasitic in the intestines, reproductive organs, or, rarely, in 

 the body cavity of invertebrates, such as crayfish, insects, and 

 worms. It absorbs liquid food from its host and has no mouth 

 nor pseudopodia. One or two individuals become encysted and 

 then break up into a number of minute portions called spores. 



The Haemosporid'ia are sporozoans which live in the blood-corpuscles of 

 vertebrates. In man they are the germs which i)roduce malaria. The 

 malaria-producing protozoans spend part of their life in man and part in a 

 certain genus of mosquito Anoph'eles). When this mosquito sucks the 

 blood of a malarial patient the germs are taken into the stomach of the 

 mosquito. " After fertilization the oosphere wanders into the intestinal 

 wall of the mosquito, grows larger, encysts, and produces many sporo- 

 blasts, which in time form many sporozoites." These pass out with the 

 saliva of the female Anoph'eles as it " bites " another person, and thus the 

 germs of malaria are transferred to his blood, where, under proper condi- 

 tions, they multiply rapidly, and fever results. It is evident that the bite 

 of this mosquito does not cause malaria unless the mosquito is itself in- 

 fected with the germs. 



Yellow fever is believed to be caused by another sporozoan carried by a 

 different genus of mosquito {Stegomy'ia). (See p. 157.) 



