SPOROZOA 



419 



formed just as has been described for H. columbce. They are very 

 slender actively motile spindles without flagella. Fertilization 

 of the macrogamete and the production of an ookinete takes 

 place in the usual manner. The latter penetrates the intestinal 

 epithelium of the mosquito (Culex sp.) and enlarges to produce 

 a spherical cyst filled with an enormous number of thread-like 

 sporozoits. These escape into the body ca- 

 vity of the mosquito as the cyst bursts, and 

 are generally distributed throughout the 

 body of the insect. They assemble, prob- 

 ably as a result of some chemical stimulus, 

 in the salivary glands of the mosquito, 

 whence they are injected into the wound as 

 the insect bites, and at once invade erythro- 

 cytes to begin the cycle of schizogony. 



The discovery of the sexual cycle of pro- 

 teosoma in the mosquito and the conclusive 

 proof that this form of bird malaria is trans- 

 mitted by a mosquito stands to the ever- 

 lasting credit of Ronald Ross. His brillant 

 discovery made in India in 1898, pointed FlG - X 9- Oocyst of 



. . Proteosoma prcscox, de- 



the way to the Solution of the whole prob- veloped on; the intestine 



of A'edes (Stegomyia) ca- 

 lopus, showing numerous 

 sporozoits. (From Do- 



flein after Neumann.} 



lem of the transmission of the malarial dis- 

 eases and their practical restriction. 



Proteosoma is a favorable parasite for 

 class study, as it is readily transmitted from bird to bird (spar- 

 rows or canaries) by injection of infected blood, and the para- 

 sites often become very numerous in the blood. There seems 

 to be no good reason for placing this organism in a separate genus 

 from the human malarial parasites. 



Plasmodium Falciparum (Praecox). Laveran in 1880 dis- 

 covered the first malarial parasite in the blood of man and cor- 

 rectly interpreted his observations. The distinctions between the 

 three species was recognized by Golgi, and the life history of the 

 parasites and especially their relation to mosquitoes and insects 



