70 HEREDITY AND VARIATION 



Persistent Peculiarities in Families. — Not less striking 

 than the long persistence of specific and stock characters 

 is the fact that offspring frequently reproduce the individual 

 peculiarities — both normal and abnormal — of their parents or 

 ancestors. A slight structural peculiarity, such as a lock of 

 white hair or an extra digit, may persist for several genera- 

 tions. A slight functional peculiarity, such as left-handedness, 

 has been recorded for at least four generations, and colour- 

 blindness for five. There are endless illustrations of the fact 

 that a pathological diathesis — -rheumatic, gouty, neurotic, or 

 the like — -may persist and express itself similarly, even in spite 

 of altered conditions of life, throughout many generations. 

 And what is true of bodily characteristics is not less true of 

 mental peculiarities : as to this, popular impressions and the 

 careful investigations of Galton and others are in agreement. 



§ 3. Different Kinds of Organic Change 



It may conduce to clearness if we think over the different 

 kinds of changes which occur in organisms. 



I. Metabolism. — All living creatures are, as it were, whirl- 

 pools in the universal ocean of matter and energy. They are 

 continually changing as they live. Streams of matter and energy 

 pass in and out. Organisms are animate systems which trans- 

 form matter and energy in a characteristic way which we call 

 living. Their physical basis is continually undergoing destruction 

 and reconstruction ; it breaks down and is built up again, it 

 wastes and is repaired, it runs down and is ever being wound up 

 again — until the arrears of imperfect recuperation become so 

 serious that the organism dies, or until some fatal accident 

 occurs. The chemical and physical changes involved in living 

 are summed up in the term metabolism, the two aspects of 

 which — constructive and disruptive — are called anabolism and 

 katabolism. 



