OF MICRO-ORGANISMS. 41 



of endeavoring to identify the attributes of living or- 

 ganic matter with the physico-chemical properties of 

 the mineral kingdom. 



In our opinion, the only question demanding con- 

 sideration is whether the choice of food, in the case 

 of Proto-organisms, does or does not result from a 

 psychical operation, similar, for example, to that which 

 takes place in higher organisms. We have received 

 a noteworthy communication from M. E. Maupas, 

 upon this subject, which tends to establish that the 

 choice of food is not the result of individual taste in 

 the Micro-organisms, but is determined by the or- 

 ganic structure of their buccal apparatus which does 

 not allow them to receive other forms of nutriment. 



We must closely examine, therefore, the mechan- 

 ism for prehension of food. 



The following is what occurs when the Amoeba, in 

 its rampant course, happens to meet a foreign body. 

 In the first place, if the foreign particle is not a nutri- 

 tive substance, if it be gravel for instance, the amceba 

 does not ingest it; it thrusts it back with its pseudo- 

 podia. This little performance is very significant; for 

 it proves, as we have already said, that this micro- 

 scopic cellule in some manner or other knows how to 

 choose and distinguish alimentary substances from 

 inert particles of sand. If the foreign substance can 

 serve as nutriment, the Amceba engulfs it by a very 

 simple process. Under the influence of the irritation 

 caused by the foreign particle, the soft and viscous 

 protoplasm of the Amceba projects itself forwards and 

 spreads about the alimentary particle somewhat as an 

 ocean-wave curves and breaks upon the beach; to 

 carry out the simile that so well represents the process, 

 this wave of protoplasm retreats, carrying with it the 



