Xl] DEVELOPMENT OF PARASITE 199 



At a temperature of 20° to 22° C. the formation of the 

 ookinete and its subsequent development is very greatly 

 prolonged, but the liberation of the microgametes and the 

 process of copulation does not seem to be delayed. 



If the humidity is lowered to about 40 per cent, the develop- 

 ment of the cysts is prolonged for at least two days, so it 

 seems that a dry atmosphere is relatively unfavourable to the 

 infection of mosquitoes. 



Fig- 53- View of the stomach of a Culex shewing large numbers of the 

 sporocysts of Plasmodium prcBCox on its walls. (After Ross.) 



Neumann kept very large numbers of Culex and fed them 

 entirely on the blood of an infected canary. Although the 

 majority of these mosquitoes were heavily infected with the 

 Plasmodium, none of them seemed to shew any ill-effects from 

 the presence of these parasites. On the other hand Koch, who 

 similarly fed a number of Culex nemorosus on birds infected 

 with P. prcBcox, found that many of the insects succumbed to 

 the infection. 



REFERENCES. 



Grassi, B. (1901). Die Malaria-Studien eines Zoologen. Jena: Fischer. 

 Koch, R. Ueber die Entwicklung der Malariaparasiten. Zeitschr. /. 



Hyg. u. Infektionskrankh. vol. xxxii. 

 Neumann, R. O. (1909). Die Obertragung von Plasmodium prcscox auf 



Kanarienvogel. Arch. f. Protistenkunde, vol. xiii. pp. 23-69. 

 Ross, R. (1905). Nobel Prize Essay, 1905. 

 Ruge, R. (1901). Untersuchungen iiber das deutsche Proteosoma. 



Centralbl. /. Bakt. i. vol. xxix. pp. 187-191. 

 Sergent, Ed. and Et. (1907). ^fitudes sur les H6matozoaires d'Oiseaux. 



Ann. Inst. Pasteur, vol. xxi. pp. 251-280. 



