FLAGELLATED PROTOZOA 53 



cyst of chitin, within which it is protected against adverse 

 conditions such as drought. When conditions are again 

 suitable the cyst wall is ruptured, and the organism comes 

 out for a new cycle of growth and reproduction. 



B. FLAGELLATED PROTOZOA. CHILOMONAS AND ALLIED 



FORMS 



When protein matter, a piece of beef or vegetable, is left in 

 water for a day or so it disintegrates and putrefies under the 

 action of bacteria. In addition to the swarms of these minute 



FIG. 20. Entamoebae from the intestine during division stages of the nucleus. 



From preparations. 



bacteria there may also appear in the water enormous numbers of 

 small flagellated protozoa, Chilomonas par amecium. Compared 

 with the smaller bacteria these minute animals are of consider- 

 able size, but compared with ^4 moeba proteus they are quite small, 

 having a length of about 25 to 30^ (Kooo to J^QO of an inch.) 

 In form they are somewhat like an elongated foot-ball with an 

 obliquely truncated end, which we may term the anterior end 

 since this is the end in advance when swimming (Fig. 21). 

 The posterior end is rounded and blunt, and has no structural 

 features of importance. The animal moves through the water 

 by means of two parallel flagella which extend out to a 

 distance equal to the total length of the body, the latter being 



