INFUSORIA 9 



between a hard substance and a softer substance suitable for 

 food, as well as to recognize their kind by contact. 



Weir, in his " Dawn of Reason," tells of observations with an 

 Adinoph'rys, in which it was seen to discriminate between starch 

 grains and uric-acid crystals. 



Protozoans are also known to be responsive to heat and light. 

 Weir also states as his opinion that all animals can distinguish 

 day from night. The question remains as to whether or not 

 this is ascertained by sight. However this may be, there can 

 be absolutely no vision, because there is no mechanism for it. 



Importance of Protozoans. — (1) They furnish, either directly 

 or indirectly, food for all higher forms of life. (2) They are 

 scavengers of decayed organic matter. (3) By their countless 

 numbers throughout the ages, vast formations of chalk or lime- 

 stone have been made. Myriads of them are still sinking to the 

 bottom of the ocean as Glob'igeri'na ooze or Radiolarian ooze. 

 Since these animals are aquatic, geologists know that wherever 

 these vast formations are found, there was once the sea. (4) 

 Some of them are parasitic in the lower animals and in man, 

 causing diseases which are ofttimes widespread and serious.^ 



Classification. — (Adapted from Parker and Haswell) : 



Clasfi. Examples. 



I. Rhizop'oda. Amce'})a, etc. 



II. Mastigoph'ora. Eugle'na, Vol'vox. 



III. Sporozo'a. Gregarl'na, etc. 



IV. Infuso'ria. Paramce'cium and Vorticel'la. 



1 Colonial Protozoa. See Jordan's "^Evolution and Animal Life," p. 217. 



