PREVIEW 607 



siderably changed or modified if a single factor is modified. Take 

 the case of the potato plant sprouting in the cellar : it is quite a 

 different organism from the one growing in its natural environ- 

 ment. Look at the differences between trees grown near the top of 

 a mountain where they are exposed to the wind and those of the 

 same kind growing on the protected slopes of the same mountain, 

 or notice the differences in the trees growing on the north and on 

 the south sides of a valley. Hundreds of examples might be given 

 to show not only that the environment determines the kind of 

 organisms living there, but also that the plant or animal may be 

 considerably modified or changed through the action of the 

 environment on it. 



But it is still somewhat a discussed question as to whether the 

 changes thus brought about will be handed down to the offspring 

 of the plant or animal. We know that seeds from a wind-blown 

 tree if they take root in a protected side of the mountain will grow 

 tall and straight like the others around it. Mice whose tails had 

 been cut off were bred for numerous generations without producing 

 any tailless offspring. Lamarck, the French naturalist, who first 

 noted that the influence of the use or disuse of organs on the organ- 

 ism is very great, followed this statement with another, that the 

 effects of such influences were handed down by heredity to the 

 offspring. Most modern experiments do not uphold Lamarck's 

 views, although there are a few that are believed to show the effect 

 of environment upon the offspring. 



We have seen that instinct plays an important part in the lives 

 of animals lower than man. A baby chick just hatched pecks at 

 a bad-tasting caterpillar and receives a sense impression, so that 

 after a few more mistakes of the same kind, it learns that such 

 caterpillars are not good and must be left alone. Man not only 

 learns to profit by experience, as does the chick, but in addition 

 he passes on this knowledge to others. While he cannot hand on 

 this knowledge by heredity, he can teach others, and they in turn 

 can teach their generation. In a similar way the human race has 

 made wonderful progress, the benefits of which we are now en- 

 joying. This great mass of experience, which results in better 

 health, better training, and material things as radios, automobiles, 



