OF MICRO- ORGANISMS. 1 1 1 



The size will not affect the matter at all. The same desires, 

 says Montaigne, stir mite and elephant alike. The psychic life of 

 the bee is as complex as that of the whale, and if amicroscopic in- 

 fusory possess eyes, mouth, prickles, and heart, it evidently pos- 

 sesses them in order that it may make us3of them, and accordingly 

 I shall treat it as a complex organism upon the same ground that I 

 do a snail or a grasshopper. Embryology will not force me to the 

 extremity of regarding such a creature as a simple organism be- 

 cause it is derived from a single cell. 



In my opinion, therefore, it is that unfortunate word unicellu- 

 lar, that has made M. Binet believe that. Infusoria being unicel- 

 lular organisms, the elementary psychology of the cellule applied 

 to them. M. Binet has allowed himself to be deceived by a word — 

 a thing that often happens in matters of science. For my own 

 part, in order to avoid any confusion, I would like to say that the 

 elementary psychology of the cellule ought not by rights to be ap- 

 plied to anything except to homogeneous cellules; for the psychol- 

 ogy that has to do with complex cells — real organisms with organs 

 and apparatus of their own — must certainly be as complex as the 

 psychology of animals wholly differentiated. 



The laws of irritability act in all their simplicity and rigor 

 among simple beings. In fact, in every instance of investigation 

 into the nature of simple org.inisms, or such as appear simple by 

 the optical instruments at our disposal (a fact that does not always 

 rigorously prove their simplicity), as bacteria, for example, — we 

 find that chemical irritability is the apparently sole law of move- 

 ment. What else, indeed, are the movements of those bacteria so 

 thoroughly studied by M. Engelmann, if not an affinity for oxygen, 

 in other words the simplest and most universal chemical phenom- 

 enon in all nature? 



And so the critique of M. Binet will not stand. On the con- 

 trary, it seems to be well established that complex organisms, 

 whether single-celled or many-celled, have a psychology corre- 

 sponding in complexity to the degree of differentiation their organs 

 have attained, while simple beings — and they are simple only if 

 homogeneous — ^have a simple psychology which is probably con- 

 tained in the laws of Irritability only. Ch, Richet. 



My reply to the letter of M. Richet, published in 

 the same number of the Revue Philosophique, may be 

 offered as a general conclusion to my work. With the 



