THE SIMPLEST, OR ONE-CELLED ANIMALS 119 



watering-trough or barrel which does not contain thousands 

 of individuals of the one-celled animals. And in any such 

 stagnant water there may always be found several or many 

 different kinds or species. A drop of this water examined 

 with the compound microscope will prove to be a tiny world 



Fig. 46. Sun animalcule, a fresh-water Protozoan with a siliceous skeleton 

 and long thread-like protoplasmic prolongations. (From life.) 



(all an ocean) with most of its animals and plants one-celled 

 in structure. A few many-celled animals will be found in it 

 preying on the one-celled ones. There are sudden and 

 violent deaths here, and births (by fission of the parent) and 

 active locomotion and food-getting and growth and all of the 

 businesses and functions of life which we are accustomed 

 to see in the more familiar world of larger animals. 



