142 DOCTRINE OF EVOLUTION 



The laws of biological inheritance have received 

 close and deep study by numerous investigators of 

 Darwinian and post-Darwinian times, because from 

 the first it was clearly recognized that a complete 

 description of nature's method of accomphshing evolu- 

 tion must show how species maintain the same general 

 characteristics from generation to generation, and also 

 how new qualities may be fixed in heredity as species 

 transform in the course of time. Before our modern 

 era in biology, the fact of inheritance was accepted as 

 self-sufficient ; now much is known that supplements 

 and extends the incomplete account given by natural 

 selection of the way evolution takes place. 



It is not possible in the present brief outline to de- 

 scribe all the results of recent investigations, but some 

 of them are too important to be passed over. Perhaps 

 the most interesting one is that the laws of heredity 

 seem to be the same for man and other kinds of living 

 creatures, as proved by Galton and Pearson and many 

 others who have dealt with such characters as human 

 stature, human eye color, and an extensive series of 

 the pecuharities of lower animals and even of plants. 



The researches dealing with the physical basis of in- 

 heritance and its location in the organism have yielded 

 the most striking and brilliant results. Darwin him- 

 self realized that the doctrine of natural selection was 

 incomplete, as it accepted at its face value the inherit- 

 ance of congenital racial qualities without attempting 

 to describe the way an egg or any other germ bears 

 them, and he endeavored to round out his doctrine of 

 selection by adding the theory of pangenesis. Accord- 

 ing to this, every cell of every tissue and organ of the 



