CHAPTER VIII 

 INHERITANCE OF ACQUIRED CHARACTERS 



THE normal characteristics of all organic beings may 

 be greatly modified by external conditions acting con- 

 tinuously upon the organism for a longer or shorter 

 period of time. Such modifications may be of so marked 

 a character as to cause an apparent departure from the 

 average or normal characteristics of the race. Through 

 accident, disease or by design, the animal or plant may 

 become permanently mutilated. The modifications which 

 result from the causes mentioned may make the domestic 

 animal or plant more useful to man than the normal 

 organism ; the changes may in fact be real improvements, 

 and as such it would be very desirable to perpetuate 

 them by heredity. Thus the breeder of domestic ani- 

 mals, having accurately observed the general fact of 

 inheritance of the normal characters, has reasoned that 

 such remarkable changes as those often resulting from 

 use or disuse, favorable environment or mutilations must 

 be transmitted with equal force. 



147. Belief in transmission of acquired characters. 

 The literature of the ancients indicates that the philos- 

 ophers of that period believed in the inheritance of 

 acquired characters. Aristotle mentions the transmission 

 of the exact shape of a cautery mark. At a much later 

 period Lamarck elaborated his theory of variation and 

 selection which took for granted that all modifications 



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