4 i 8 THE POPULAR SCIENCE MONTHLY 



obvious, though how easy of application remains to be ascertained. 

 Would a farmer expect to have full harvests if each year he saved seed 

 from the poorest yielding plants, or could he hope to secure the best re- 

 sults from his herds by selling or butchering the best stock and keeping 

 only the scrubs? Obviously not, and no more can the civilized nations 

 maintain their present standards of manhood if they follow a like 

 practise. 



But before any serious attempt can be made to improve the human 

 race considered as an assemblage of animals possessed of certain de- 

 sirable physical and intellectual attributes, it is obvious that we must 

 know something about heredity in general, and how in particular each 

 of the desired physical and intellectual attributes is produced. Con- 

 siderations such as these lend general interest to the study of heredity, 

 a subject which has always been of great practical concern to farmers, 

 and of much theoretical interest to scientists. It is my purpose to 

 review briefly some of the problems which the study of heredity pre- 

 sents, and some of the results obtained from their consideration. 



" Like father like son " is a homely proverb which shows how 

 general the recognition is that children resemble their parents. Re- 

 semblances to grandparents or ancestors even more remote are also of 

 frequent occurrence, and it is convenient to use the term heredity as 

 including all such resemblances, whether to near or to remote ancestors. 

 The phenomenon of heredity is of course not restricted to human 

 society. Heredity has for the stockman and plant-breeder a well- 

 recognized commercial value, because by a knowledge of its laws he is 

 enabled to produce in greater number or with greater certainty animals 

 or plants of a particular type. Indeed, much of our present knowledge 

 of heredity has been derived from a study of the domesticated animals 

 or of the cultivated plants, and from the same sources we may expect 

 to continue to draw, for here alone have we an unobstructed field for 

 observation and experiment, the indispensable tools of scientific re- 

 search. Just as the sciences of anatomy, embryology, physiology and 

 pathology progressed but slowly so long as the phenomena of the human 

 body alone were considered, but advanced by leaps and bounds when 

 comparative studies on other animals were undertaken, so concerning 

 heredity in man we have learned and can expect to learn but little from 

 the study of man alone, but much from a study of other animals and of 

 plants and from a comparison of the phenomena in the two cases. 



Every new individual arises out of material derived exclusively from 

 its parents. This is the basis of heredity. But it does not follow that 

 the new individual will resemble its parents merely. It may resemble 

 remote ancestors more strongly than either parent. For it represents 

 a combination of materials or of qualities derived from the two 

 parents and it is possible that neither parent may manifest all the 



