134 THE MAIN CURRENTS OF ZOOLOGY 



undergo a development in the walls of the stomach 

 of the mosquito. The conjugation is a sort of fer- 

 tilization such as occurs in all animals and plants, but 

 it will not take place in human blood. A " secondary 

 host" is necessary in which to complete the life 

 cycle. After fertilization the developing forms pro- 

 duce nodules on the walls of the stomach of the 

 mosquito and in these nodules takes place the 

 transformation into spindle-shaped forms which get 

 into the salivary ducts of the mosquito. When 

 biting, the mosquito injects some of these into the 

 blood of the victim and there they begin to multiply 

 rapidly by asexual budding. 



Doses of quinine are used to kill the malarial 

 parasite. 



Studies of the development of the mosquito soon 

 led to methods of protection. Mosquitoes breed in 

 water a small quantity being sufficient . Protection 

 comes from draining marshes, getting rid of pools and 

 of containers of exposed water, and from spraying 

 with crude petroleum so that the wigglers which 

 hatch from the eggs can not get air, and conse- 

 quently, the mosquito can not come to its full devel- 

 opment. The use of screens and remaining indoors 

 after sundown are also wise measures of precaution. 



