OF MICR O- OR GANISMS. 39 



solar radiations, executed movements and set out- 

 wards in all directions. 



2. Nutrition by endosmosis, or saprophytic. The or- 

 ganism nourishes itself by absorbing through the 

 whole surface of its body liquids containing the pro- 

 ducts of vegetable or animal decomposition. Sapro- 

 phytic beings are found in putrid waters or in infu- 

 sions. This manner of nutrition may be considered, 

 from the point of view which now engages us, as the 

 most simple of all; it probably allows of a search for 

 food, but it is certain that no movements are involved 

 which are designed to draw the food into any possible 

 digestive apparatus. 



3. There is now a last mode of nutrition, of which 

 we shall treat in minute detail; namely, animal nu- 

 trition, where the Micro-organism seizes solid alimen- 

 tary particles and nourishes itself after the fashion of 

 an animal, whether it be by means of a permanent 

 mouth or by means of an adventitious one, improvised 

 at the moment of need. This manner of nutrition is 

 the process employed by higher animals. Among the 

 lower organisms, it is met with in most of the In- 

 fusoria, in the Sarcodines, in many of the Mastig- 

 ophores, and in others. Respecting the Micro-organ- 

 isms belonging to the vegetable kingdom, we find 

 nutrition by endosmosis and chlorophyl nutrition; 

 the Protophytes never possess a mouth and never 

 absorb solid foods. 



Animal nutrition requires very remarkable psy- 

 chological faculties in the organism practicing it. 

 These manifestations of psychic life, the progressive 

 complexity of which we intend to trace in starting 

 from the simplest protozoic forms and arriving at the 

 higher prove that these animalcula are endowed with 



