fluenced by its activities or its experiences; muscles grow more if they are 

 used more. (2) Organisms, and especially animals, adjust themselves to their 

 surroundings in the course of their lives — for example, a mature animal is 

 better fitted to supply its needs or protect itself than it was in its younger 

 stages; a child exposed to sunshine will come to have a darkened skin. 



From his reflections, Lamarck concluded that "all that has been acquired, 

 begun, or changed in the structure of an individual in the course of its life is 

 preserved in reproduction and transmitted to the new individuals which spring 

 from that which has experienced the change." 



This view, widely held, appears quite reasonable. It "explains" the long 

 neck of the giraffe, for example. By stretching to reach the leaves on trees, 

 the ancestors of this species pulled their heads higher and higher above the 

 ground, the argument runs. In any particular generation the stretching may 

 have been very slight, but this little gain was inherited by the offspring. They, 

 in turn, added a little to their height in the same manner. And this process, 

 continuing generation after generation, resulted in the long-necked animal we 

 know today. 



This theory can also explain the webbed feet of water birds. A young bird 

 thrown into the water would naturally spread its toes as far as possible to ex- 

 pose the maximum surface for paddling. As the animal continued to stretch 

 its toes apart, the skin between them would gradually spread, resulting after 

 many generations in the webbed foot of the duck or goose. 



Lamarck's views appeal to many as common sense. "It stands to reason" 

 that the gains which are made in the course of a generation should benefit the 

 following generation. The analogy from society is impressive. Those who are 

 industrious and thrifty and accumulate more than their neighbors naturally 

 "pass on" more to their children; the latter inherit more. A good home 

 gives children a good start. And they in turn, when they grow up, provide 

 better homes for their children. Communities that have good schools, for 

 example, progress more rapidly than those without schools or with poor 

 schools. Well-nourished plants produce larger seeds, and larger seeds grow 

 into better plants, which in turn produce larger seeds. It all "stands to rea- 

 son." But what are the facts? 



Objections to Lamarck's Explanation We may grant that his experi- 

 ence and activities modify the individual in the course of his development, or 

 that the new species appear to be as well adapted to their surroundings as 

 their ancestors probably were. Lamarck's argument is nevertheless far from 

 conclusive, for in it is concealed an assumption which may turn out to be 

 unwarranted. Are the effects of experience or activities actually transmitted to 

 the offspring? Is bUndness resulting from injury to an eye reproduced in one's 

 children? Is the effect of a broken leg or of practice on a piano inherited? The 

 sons of blacksmiths may have better muscles than the sons of bookkeepers, 



465 



