286 Heredity. 



and light. A little small-pox virus in the organism will produce 

 very numerous morbid phenomena. An economic reform will 

 lead to many industrial and social consequences. Everywhere, in 

 short, even when the cause is simple, the effects are manifold. 



Evolution thus understood, and both as to its law and as to its 

 cause reduced to * a purely physical interpretation ' of phenomena, 

 offers a scientific character which is not possessed by the current 

 doctrine of progress. Then, too, the latter, being concerned only 

 with human welfare, and considering that as the final cause of all 

 change, finds itself much embarrassed in view of sundry incontest- 

 able facts which show that humanity at certain periods stays and 

 retraces its steps. Evolution explains these facts. The develop- 

 ment theory, as Lyell well observes, implies no necessary progres- 

 sion. It is possible for a new race to be of simpler structure, and 

 of less developed understanding, than those which it displaces ; a 

 slight advantage is sufficient to insure it the victory over its rivals. 

 The law of evolution accounts equally well for progress and for 

 what is called degradation that is, a retrograde movement towards 

 an inferior structure, or a lower form of dynamism. It is sufficient 

 if a being so degraded, whether physically or morally, is better 

 adapted to its new conditions of existence than a being more highly 

 endowed. 



Now that we have fixed a precise meaning on the words evolu- 

 tion, development, and progress, we can see how this law governs 

 the whole question of the consequences of heredity. In this 

 portion of our work we propose to show how heredity has con- 

 tributed to the formation of certain intellectual or sensitive 

 faculties, and of certain moral habits. We can now have a 

 glimpse of this truth. Heredity and evolution are the two neces- 

 sary factors of every stable modification in the domain of life. 



Suppose evolution without heredity, and every change becomes 

 transitory : every modification whatever, whether of good or bad, 

 useful or hurtful, disappears with the individual. Evolution con- 

 fined within these narrow limits, loses all significance and all force ; 

 it is nothing but an accident, without any value. 



Suppose heredity without evolution, and there is nothing but 

 the monotonous conservation of the same types, fixed once for all. 

 Physiological characters, instincts, intellectual and moral faculties, 



