436 THE MAINTENANCE OF SPECIES 



Long ago Semper demonstrated, for example, that the size to which 

 fresh-water snails will grow is somewhat dependent upon the spacious- 

 ness of the aquarium in which they are kept, and Baur has shown 

 that red-flowering primroses may be made to produce white flowers 

 if subjected to continuous high temperature (30° C.) for a week or so 

 immediately before blooming. 



The heredity factor is so important, nevertheless, that organisms 

 can after all breed only their own kind, regardless of the environment 

 in which they are placed. It is quite as futile, therefore, to argue the 

 relative importance of heredity and environment as it would be to 

 debate which of the two surfaces of a sheet of paper is more essential 

 in making it a sheet of paper. Naturally the biologist is impressed 

 with the contribution which heredity makes in the formation of a new 

 individual, while the sociologist, as would be expected, emphasizes 

 the environmental factor. Although no seed is so poor that it may 

 not be improved by good soil and nurture, and no seed is so good that 

 it will not imperfectly develop in poor soil, yet it is not within the 

 capacity of tares under any circumstances to produce wheat, nor can 

 we expect dogs to engender cats. Former President Lowell of Harvard 

 once said, "There is a better chance to raise eaglets from eagle eggs in a 

 hen's nest, than from hen's eggs in an eagle's nest." Neither heredity 

 nor environment is effective alone. In the formation of any individual 

 organism, the environment is the force that works from without in, 

 while heredity works from within out. Both are as indispensable in 

 producing a plant or an animal as land and water are in the formation 

 of a shore line. 



Moreover, there is extra-biological or social inheritance to reckon 

 with, that makes us the "heirs of the ages." CiviHzation in itself 

 may be regarded as the collective achievements of mankind, and 

 as time goes on these environmental collections multiply and accu- 

 mulate. We live today, for example, in a world of skyscrapers, 

 automobiles, stock exchanges, airplanes, chain-stores, movies, ocean 

 liners, and radios, the acquisition of which our ancestors of three 

 hundred years ago never even dreamed of. If we may seem to have 

 a larger horizon and to sec farther than our ancestors, it is not so 

 much because we are taller than they were, as it is because we stand 

 on their shoulders with respect to these extra-biological acquisitions. 



There is no doubt that the environment of mankind has undergone 

 more modification than human heredity has. When we consider, for 

 example, the intellectual and artistic output of ancient Greece, a small 



