SCHEME OF LIFE-HISTORY 



145 



own, but in some way or another they make their way 

 into the salivary glands of the insect and accumulate 

 in the cells which secrete the saliva. Thence the 

 blasts pass into the salivary duct and down the grooved 

 proboscis of the insect (Fig. 3, No. 4). The next time 

 the mosquito has a meal off a man, some of these 

 blasts will be washed into the man's blood by the 

 saliva which causes the irritation set up by a mos- 

 quito's bite. It is known that when an infected insect 

 bites a healthy man malaria ensues ; and though the 

 blasts have not hitherto been seen to enter the blood- 

 corpuscles, they certainly give rise to the disease, and 

 it can hardly be doubted that they force their way into 

 the red corpuscles and form the young amoebulae 

 which we described at the beginning of this article. 



The appended scheme will perhaps make clear the 

 very diverse phases of the somewhat polymorphic 

 organisms. Those stages which occur in the blood of 

 man are printed in ordinary type, but those which 

 occur in the mosquito are in italics : 



AMCEBULiE. 



Sporocyte. 



Spores 

 (in liquid of blood). 



Amoebulae. 



Sporocyte. 



Spores 

 and da capo. 



Female Gametocyte. Male Gametocyte. 



Female Gametocyte. Filamentous bodies or 

 Spermatozoa. 

 ^1 



Zygote. 



I 

 Meres. 



I 

 Blasts. 



Amoebulae. 



Sporocyte. Female Gametocyte. Male Gametocyte. 



10 



