556 EVOLUTION, GENETICS, AND EUGENICS 



matter in an article in The Scientific Monthly for September, 1924, entitled Heredity 

 and Environment. As Professor Jennings puts it: "Clearly it is not necessary to 

 have a characteristic merely because one inherits it. Or more properly, character- 

 istics are not inherited at all; what one inherits is certain material that under certain 

 conditions will produce a particular characteristic; if those conditions are not 

 supplied, some other characteristic is produced." 



In this sense a man's knowledge of Latin grammar is just as much an inherited 

 character as is his bald head. Both developed because certain packets of chemicals 

 called factors were in the germ-cell from which he was bom, and these factors 

 under the conditions that he met in life developed into these characteristics. Had 

 he met different conditions he would have developed other characteristics in their 

 stead. It is not true that a man is predetermined in or by the germ-cell and that 

 a foreordained man with foreordained characteristics is going to grow up willy- 

 nilly. However, because of merely practical difficulties we can not very radically 

 alter men by education and environment, partly because we do not as yet have the 

 proper technical means and partly because the environment is fairly uniform for 

 all human beings during the first nine months of their lives and they come into the 

 world as quite far advanced organisms. But in frogs and fruit flies and other ani- 

 mals where the egg itself and the early embryo can be radically interfered with,, 

 changes can easily be produced which make the adult animal strikingly different 

 from what it would have been in the usually expected environment. We predict 

 a certain kind of man by studying his ancestry merely because we expect for him 

 a certain tjrpe of general environment not profoundly different from that of his 

 ancestors. It is the expected enviromnent which leads us to count pretty strongly 

 on heredity and not that the heredity in the germ package predetermines all he shall 

 be. F. A. Woods pointed this out nearly fifteen years ago. Of course there are 

 limits to the alterations possible by envirormient, but they are far from being reached 

 as yet with human beings. None of this alters the fact that very moderate environ- 

 mental measures, such as education and moral suasion, expended on rich hereditary 

 material yield far greater results than when expended on poor material. Other 

 measures might produce as marked results with poor material, but in society as 

 a practical matter there is neither the time nor money as yet to try to make imbeciles 

 into geniuses when by proper marriages they can be produced free of charge. The 

 differences among men are, I think, largely due to differences in the original heredi- 

 tary packets in the germ-cells because so much of the environment of men is common 

 io them all. I can not reproduce all of Professor Jenniags' fine presentation and 

 can only urge the thoughtful to study it with care as the most penetrating dis- 

 cussion of the heredity-environment problem that has been made from the stand- 

 point of a geneticist and embryologist. 



