PHYLUM PROTOZOA 47 



carried by the circulatory system to various parts of the body 

 including the salivary glands (27). From this location they are 

 able to pass along the hypopharynx and thus are introduced into 

 the blood stream of any human being bitten by the mosquito. 



Several different kinds of malaria are distinguishable both from 

 clinical evidence and from morphological and developmental 

 differences of the causal organisms. Spring tertian or benign 

 malaria, of which Plasmodium vivax is the cause, is characterized 

 by the presence of a fever recurring on alternate days. The 

 quartan type of malaria, which is caused by P. malariae, is dis- 

 tinguished by fevers with two-day intervals between attacks. 

 Infections of Lavcrania falciparum produce malignant or perni- 

 cious malaria with daily recurrence of the fever. 



Subclass Neosporidia 



Members of this subclass are multinuclear in their adult stage. 

 Spore production is continued over a considerable period of time 

 so that in any one individual, spores in different stages of develop- 

 ment are to be found. Unlike the Telosporidia, spore formation 

 does not bring the life of the individual to an end. Spore forma- 

 tion is indirect, for the body forms a number of sporoblast mother 

 cells. These in turn give rise to the sporoblasts which become 

 transformed into the spores. 



The Neosporidia include the Myxosporidia parasitic almost 

 exclusively on fishes, Microsporidia in insects but occasionally 

 in fishes, and the Sarcosporidia in muscle cells of mammals. Of 

 the Myxosporidia many species invade the gills, integument, and 

 muscles of fishes producing conspicuous cysts filled with minute 

 spores. The Microsporidia have considerable economic interest, 

 for the pebrine disease of silkworms is a serious menace to the 

 silk industry and the Nosema disease attacks honey bees. 



Fig. 29. — Life cycle of Plasmodium vivax, the tertian malarial parasite. Stages 

 1-12 and 13c-17c in human blood stream; stages 13a-14a, 136-156, and 16-27, 

 in body of mosquito. 1, the infecting stage for man, the sporozoite; 3-7, stages 

 in schizogony resulting in the formation of merozoites (7). 9a-12a, formation of 

 macrogametocyte; 13a— 14a, maturation of microgamete. 96-126, formation 

 of microgametocyte; 136-156, maturation of the microgametes. 16, fertiliza- 

 tion; 17, zygote or ookinete. 18-25, stages in development -wathin cysts in 

 stomach wall of mosquito; 26, sporozoites liberated from cysts making their way 

 through the body fluids to the salivary glands of the mosquito (27), where they 

 are ready to infect a man bitten by the mosquito. 13c-17c, stages in formation 

 of merozoites from macrogametocyte which fails to leave the human body. 9a 

 and 96-(25) are stages in sporogony. (From Liihe after combinations of drawings 

 by Graasi and Schaudinn). 



