30 MENDELISM 



are essentially double in every character. This may be repre- 

 sented diagrammatically (see opposite page). Let A and B 

 represent two germ-cells, which we will assume (for the sake 

 of simplicity) to contain only 4 factors each (a, b, c, d, and 

 e,f,g,h). Then C will represent the resulting individual. 

 We see that it contains the two similar factors a and e, and 

 is pure-bred for this quality. It is also pure-bred for the two 

 bottom factors, but in respect of each of the other factors 

 it is cross-bred, for it has only one dose of each. Suppose 

 this individual to be a man, then he is fortunate if the top 

 factors (black) are good qualities, and also if the bottom 

 (white) factors represent defects which are absent. But 

 what if a and e are bad qualities — a tendency to tuber- 

 culosis, mental defect, idleness, intemperance, or crime ? 

 How can an individual battle against such an inheritance ? 

 I leave you to think this out for yourselves. 



Mendelism has thrown a great deal of light upon some 

 hitherto obscure subjects, and, to say the least, it is a good 

 working hypothesis. 



I submit that the various facts that have been mentioned 

 point out, with unmistakable clearness, the only way by 

 which hereditary disease can be eliminated, and the kind of 

 stock which should be produced. We hear now-a-days a 

 great deal about physical deterioration, and much benefit is 

 expected from education and from improved sanitary laws, 

 but neither education nor sanitary laws can eradicate 

 hereditary disease, except by preventing the marriage of the 

 affected individuals. Just as a purely short-fingered race 

 could be produced, so it would be equally easy to eradicate 

 this abnormality by preventing the mating of the abnormal 

 individuals, and there is little doubt that other hereditary 

 diseases and defects can be made to practically disappear 

 by the same means. Unfortunately modern legislation 

 tends to produce the opposite effect, for everything is done 



