34 THE PSYCHIC LIFE 



low cellules, the maximum action is in the green; in 

 the case of bluish green cellules, in the yellow; in the 

 case of red cellules, in the green. The author has 

 concluded from this that there exists a series of col-, 

 oring substances which, like chlorophyl, have the 

 power of resolving carbonic acid gas; he calls them 

 chromophyls. In the same way, moreover, this method 

 enables us to solve the question of the distribution of 

 energy in the solar spectrum. As M. Engelmann has 

 remarked, it is interesting to see the Bacteria come to 

 confirm our theories as to the composition of solar 

 light. 



Bacteria are not the only organisms that eagerly 

 make towards points where oxygen is to be found. 

 A large number of other Micro-organisms act in the 

 same way when they happen into a medium lacking 

 oxygen. M. Ranvier has noticed that if a preparation 

 containing leucocytes, screened from air, be examined 

 for a certain length of time the cellules will be seen to 

 throw out long filaments towards the part that faces 

 the air-side of the preparation. It appears, then, that 

 a rudimentary oxygen-sense exists in the protoplasm 

 of Proto-organisms. 



This sense does not merely apprise the organism 

 of the presence of oxygen; it enables it, further, to 

 gauge the tension (expansive power) of the gas. So 

 that, when the tension becomes too powerful, the or- 

 ganisms are seen to flee before it. 



III. 



The mode of nutrition among Micro-organisms is 

 not uniform — a fact which ought not to appear remark- 

 able when we bear in mind that this immense group is 

 made up of all manner of heterogeneous beings that 



