PHYLUM PROTOZOA IN GENERAL 



75 



this development to go on in the mosquito. These little parasitic 

 sporozoites make their way to the salivary gland of the mosquito 

 where they may remain for weeks. When tliis mosquito ' ' bites ' ' a man, 

 some of the saliva with sporozoites flows into the wound, and the 

 process of asexual multiplication begins over again in the red cor- 

 puscles of this person as a new host. 



Colonial Protozoa 



There are some species of Protozoa in which the individual cells 

 exist in groups called colonies. This formation frequently results 

 from incomplete separation of the cells following division. In some 



Codonosi^a 



Carchejium 



Fig. 30. — Different types of colonial Protozoa. Eudorina, a simple colony; 

 Pandorina, within gelatinous envelope ; Ceratium, a linear colony ; Carchesium, 

 stalked infusorian colony; Codonosiga, a stalked flagellate colony. (Drawn by 

 Joanne Moore.) 



of these forms only two cells adhere, but in others the cells may 

 remain attached after many divisions, with the result that thou- 

 sands of cells are built into the group. In. some species there is a 

 jellylike, spherical envelope inside of which the colony of cells 

 remains. In certain species the cells are stalked, and the new cells 

 remain attached to the stalk, giving a branching colony. Pan- 

 dorina and Eudorina are typical examples of the former, while 

 Epistylis and Carchesium are typical examples of the latter. These 

 types of colonies are known as spheroid and arhoroid or dendritic 

 respectively. Colonies like that of Ceratium with individuals ar- 



