OF MICRO-ORGANISMS. 35 



have nothing in common save the microscopic little- 

 ness of their bodies and the simplicity of their 

 structure. Three main types of nutrition may be 

 briefly distinguished. 



I. Vegetable nutrition, or according to Biitschli's 

 expression, holophytic. This is the method of nutri- 

 tion among animal or vegetable cellules that contain 

 chlorophyl and that nourish themselves by forming 

 organic nutriment from ingredients taken from the 

 surrounding medium. It is hardly necessary to call 

 to mind that the function of chlorophyl is that of nu- 

 trition and not of respiration. This phenomenon was 

 formerly termed the diurnal respiration of plants. The 

 expression involves several mistakes. Enough to say 

 that vegetables respire as animals do, by uniting with 

 oxygen, and that that respiration continues the same 

 both day and night. The function of chlorophyl is by 

 no means respiration; its office is to decompose the 

 carbonic acid gas of the air and to seize the carbon, 

 which serves the plant in forming ternary or qua- 

 ternary substances. This chemical work is performed 

 by all chlorophyl organisms when influenced by the 

 radiation of light. 



Chlorophyl does not belong exclusively to the veg- 

 etable kingdom. A large number of animal Micro- 

 organisms are colored green by this pigment; they are 

 met with principally in the important group of Fla- 

 gellates. Their assimilative organs, which are like- 

 wise found in all green plants, bear the name of chro- 

 matophores; they have lately formed the subject of 

 interesting investigations. • 



The chromatophores are small bodies of protoplasm 

 which are distinguished from protoplasm in general 

 by their having assumed an individual structure. 



