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 generations. A slight functional 

 peculiarity, such as left-handedness, has been recorded for at 

 least four generations, and colour-blindness for five. The strong 

 under-lip of the Hapsburgs persisted for six centuries. There are 

 endless illustrations of the fact that a pathological diathesis — 

 rheumatic, gout}', neurotic, or the like— may persist and express 

 itself similarly, even in spite of altered conditions of life, through- 

 out many generations. And what is true of bodily characteristics 

 is not less true of mental peculiarities : as to this, popular im- 

 pressions and the careful investigations of Galton and others are 

 in agreement. We think at once of cases like the Bachs, the 

 Bernouillis, the Darwins ! 



§ 3. Different Kinds of Organic Change 



It may conduce to clearness if we think over the different 

 kinds of changes which occur in organisms. 



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

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

 continual!}' changing as they live. Streams of matter and energy 

 pass in and out. Organisms are animate systems which transform 

 matter and energy in a characteristic way which we call living. 

 Their physical basis is continually undergoing disruption 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 



