24 



Insects and Disease 



cretory processes by osmosis, i. e. y through the 

 body-wall ; all are capable of some kind of locomo- 

 tion, some have one or more flagella, others move 

 by a pseudopod movement. Some are capable of 

 moving from cell to cell in the body as do the 

 white blood-corpuscles. They all agree in the pro- 

 duction of spores — hence the name. 



At certain stages in their development the nu- 

 cleus within the body of the organism divides again 

 and again until there are a great many daughter 

 nuclei, each accompanied by a small mass of proto- 

 plasm, often inclosed in a little sac or cyst of its 

 own. This is the process of spore-formation and 

 we see that from a single individual we may have 

 by division, not two animals as in the amoeba, but 

 a score or more of them. The little cysts or 

 capsules that inclose them enable them to resist 

 without injury many vicissitudes that would other- 

 wise destroy them. They may dry up or freeze or 

 lie for a long time in the ground or water until the 

 time comes when they are introduced into another 

 host. 



The class Sporozoa is divided into five small 

 groups or orders. Nearly all of these contain 

 forms that are of more or less importance, but the 

 ones that live in the blood-cells (Hcemosporidiida) 

 are of the most interest to us because the parasites 



