200 UNIVERSAL EVOLUTION 



be the ones to produce eventually another and still 

 other variations of more complex nervous structure. 

 The survival all the time of the best adapted, or the 

 fittest, would end in a superior psychophysical unit. 



Upon this theory, it becomes at once apparent, that 

 the great variety of intelligence, or mentality, we see 

 in animal nature, has been caused by the simultaneous 

 variation of structure, and of the function thereof, in 

 all the innumerable organisms of every line of descent, 

 in the organic kingdom. 



For example, two blades of grass, almost side by side, 

 will often show a great difference in growth, because 

 the rapid growing one happens to be in contact, at its 

 roots, with a richer food, than its near neighbor, this 

 richer food being a part of its environment ; and 

 immediately its function, to take in more and more 

 sustentation, grows simultaneously with its parallel 

 development of root and stem structure, until it over- 

 shadows its puny neighbor, whose structure remains 

 adapted only to its function to take in the smaller, and 

 less nutritious sustentation. This puny blade lacks the 

 environment of richer food of its more fortunate neigh- 

 bor. The former produces large and vigorous seeds, 

 in correspondence with its larger function of sustenta- 

 tion; while the seed, of the weaker blade, will barely 

 germinate at all, and perhaps dies out. But the differ- 

 ence between the successive generations of the two 

 blades of grass, for all the time they may exist, is 

 caused by the habits, or functions, begun by the two 

 original blades, the difference of function producing 

 the visible difference of structure. Weissman 's theory 

 of heredity includes just this principle of variation. He 

 seems to think variation is the result of the larger 

 difference in sustentation received by the biopher. pro- 



