80 THE SURVIVAL OF THE UNLIKE. [h. 



is a general and strong conviction that many truly ac- 

 quired characters are hereditary, and there seems to be 

 demonstrable evidence of it; and while sex variation is 

 fully accepted, it logically follows, if acquired characters 

 are hereditary, that much variation is due directly to 

 external causes. Perhaps the habit of thought of most 

 Darwinians and Neo-Lamarckians is something as 

 follows : 



All forms of life are mutable. Variation affords 

 the material or starting-points from which progress is 

 derived. Variation is due to sexual union, changed 

 conditions of life, the energy of growth, panmixia or 

 the cessation of natural selection, and to direct use 

 and disuse, although use and disuse are minor factors 

 amongst plants. There is an intense struggle for ex- 

 istence. All forms or variations useful to the species 

 tend to live, and the harmful ones tend to be destroyed 

 through the operation of the simple agent of natural 

 selection. These newly appearing forms tend to be- 

 come permanent, sometimes immediately; but the longer 

 the transforming environments are present, the greater 

 is the probability, on the whole, that the resulting 

 modifications will persist. 



