PPvOTOZOOLOGT 



T 



CHAPTEE I. 



GENERAL ORGANIZATION OF THE PROTOZOA. 



A PROTOZOON is a primitive animal organism usually consisting of a 

 single cell, whose protoplasm becomes distributed among many free 

 living cells. These reproduce their kind by division, by budding, or by 

 spore formation, the race thus formed passing through different form 

 changes and the protoplasm through various stages of vitality collec- 

 tively known as the life cycle. ^ 



Fig. 1 



Types of protozoa. A, Ameba proteus, a rhizopod (after Calkins); B, Peranema trichoph- 

 orum, a flagellate (after Biitschli) ; C, Stylonychia niytilis, a ciliate with specialized cilia (after 

 Biitschli): E, Tokophrya quadripartita, a suotorian (after Biitschli); D, Pyxinia, sp., a poly- 

 cystid gregarine with primite and deutomerite (after Wasielewsky) ; c, contractile vacuole; e, 

 epithelial host cell; n, nucleus; v, food vacuole. 



It is quite impossible within the limits of a small volume to give a 

 detailed or even adequate account of the many sides of interest of the 

 unicellular animals. The wide range in habitat, from the purest 

 waters of lake or sea to the foulest ditch, or the adaptation to environ- 

 ments varying in character from a mountain stream to the semifluid 

 substance of an epithelial nerve or muscle cell, has brought about 



1 Definition by Calkins, 1906. 



