PROTOZOA. 151 



compound later dividing into two equivalent individuals. 

 Here we have true sexuality. 



The classification of the Infusoria is based upon the 

 character of the appendages developed from the body. 

 Only the two most prominent groups are mentioned. 



Order I. Flagellata. With one or more flagella (fig. 6). 

 Some of these forms are clearly animal, while allied species 

 are claimed by the botanist. Some are naked , some have 

 collars around the flagellum, and others have cases in which 

 the animal is placed. Some swim freely and some are at- 

 tached; among these latter colonies consisting of several 

 or many individuals are common, these arising by incom- 

 plete division. Some live in fresh water, others are marine. 



Order II. Ciliata. Numerous cilia either over the w r hole 

 body or restricted to certain areas. The ciliates occur 

 in both salt and fresh water and include some of the largest 

 Protozoa. Some swim freely, some creep about on large 

 modified cilia (fig. 7), and some are attached. Most 

 familiar are the genera Paramcedum, Vorticella, and Stentor. 



CLASS III. SPOROZOA. 



These degenerate forms were long neglected, but within 

 recent years they have attained great prominence because 

 of the relations to certain diseases. All are parasitic 

 inside other animals. They lack all external cell-organs, 

 and most of them, except at the time of reproduction, 

 are without powers of motion. The name Sporozoa refers 

 to the fact that in reproduction these Protozoa break up 

 into a number of small bodies called spores. Most 

 important of the Sporozoa is Plasmodium laverani (fig. 8), 

 which is introduced into the human blood by mosquito 

 bites and there lives parasitic in the blood-corpuscles, 



