VI. SUBKINGDOM PROTOZOA. 



General Characteristics. — The Protozoans (first ani- 

 mals) are small, aquatic, mostly microscopic unicellular 

 animals. They are composed of a mucous, albuminous 

 substance called protoplasm. As yet, neither nerves, mus- 

 cles, circulatory or digestory organs have been discovered. 

 They, however, apparently possess the functions of animal 

 life — motion, sensation, nutrition, and reproduction. In- 

 numerable Invertebrates feed upon them. The "Edible- 

 earths" and "Infusorial-earths" probably owe their nutri- 

 tive value to the remains of Protozoans. All subdivisions 

 are provisional. 



CLASS INFUSORIA. 



General Characteristics. — The Infusoria (originating 

 in infusions) include a large variety of microscopic animal- 



Mn m cules found in vegetable infusions that have 

 been left exposed to the air for a few days. 

 Their presence is doubtless due to the dried 

 bodies of their ancestors or minute germs float- 

 ing in the air till a lodgment in the infusion 

 favors development.* 



Vorticels (vortex) are types of fixed forms. 

 To the naked eye they are simply mold on the 

 stem of a plant ; but in the microscope the mold 

 becomes a forest of single animalcules, each 



TorticeUa. attached by a stem several times its own length, 



* Ee-moistening the hard, haked mud from the bottom of a dried-np pool is found 

 to rc-vivify them in innumerable quantities. " Theee Infusoria," says Figuier, " may 

 be and are without doubt carried to great distances, for an indefinite period of time, 

 r.nd then, abandoned on some ledge of rock, on a housetop, in the cleft of a wall, or 



