THE PSYCHIC LIFE OF MICRO-ORGANISMS. 



THE study of microscopic organisms has hitherto 

 been somewhat neglected by students of comparative 

 psychology. Naturalists who have devoted their at- 

 tention to the study of these beings, have collected a 

 great number of interesting facts concerning their 

 psychic life; but these facts have not yet been critically 

 examined and collated; they are scattered in reports 

 and publications of all kinds, where the psychologist 

 never dreams of looking for them. We shall endeavor 

 to make him acquainted with a part of this wealth. 



Under the name Micro-organism are included all 

 those beings which by reason of their extreme smallness 

 and simplicity of structure represent the lowest stages 

 of animal or vegetable life; they constitute the very sim- 

 plest forms of living matter, and consist of a single cell. 

 Some inhabit fresh and salt waters, serving as food 

 for a great many other organisms, or contributing by 

 means of their calcareous or silicious skeletons to the 

 formation of continents. Others live as parasites in 

 the organs of animals and plants, and induce more or 

 less serious disorders in the constitutions of the organ- 

 isms they have penetrated. Others, again, acting like 

 ferments produce important chemical modifications in 

 organic matter in the course of decomposition. 



A great number of classifications for the methodical 

 distribution of these beings has been proposed; but 

 not one of them is altogether satisfactory; and that 



