198 Education through Nature 



ganisms remain near the surface, where the air comes 

 in contact with the water. 



But, even in the presence of a constant supply of 

 food and oxygen, by which the wasted elements are 

 again repaired by nutrition, assimilation, respiration, 

 and excretion, this constant activity cannot continue 

 indefinitely. The mere lapse of time seems to have 

 a specific effect on protoplasm, causing it to grow old 

 and incapable of maintaining an equilibrium between 

 waste and repair. In the case of many of these uni- 

 cellular forms this inevitable senility is partly over- 

 come by conjugation, the interchange of nuclear mate- 

 rial of two distinct individuals. They are consequently 

 rejuvenated periodically. They are thus again capable 

 of multiplying by division, and are supposed to be in 

 a sense immortal. 



Even in these unicellular forms, therefore, we per- 

 ceive that each individual has two very important 

 functions to perform that of maintaining itself and 

 that of maintaining the race of beings to which it 

 belongs. It is neither wholly selfish nor wholly altru- 

 istic, but a little of both. All of their activities seem 

 to have in view these functions, and the success with 

 which the work is performed seems to depend on the 

 success with which an internal adjustment is main- 

 tained with reference to the surrounding medium. 



Being as yet wholly ignorant in regard to the essen- 

 tial nature of both life and mind it would of course 

 be absurd to try either to prove or to disprove their 

 universal coexistence. Yet it is clear here that what 

 we interpret as life and what appears to us as mental 

 manifestations are so intimately united that a distinc- 

 tion between them is impossible. Both the vital 

 and the mental processes, if such there be, are con- 

 cerned with such an adjustment of the organism to 

 external condition as shall enable the organism to 

 exist. 



