Heredity. 



to its essence ; hence it is perfectly natural that all these 

 qualities and modifications should be transmitted to its descend- 

 ants. But man cannot, any more than other animals, live without 

 contracting habits ; without undergoing, under the influence of 

 circumstances, or from an excess or deficiency in the exercise of 

 each organ, modifications of all kinds, which remain fixed in him. 

 Are these transmitted? Are they destined to perish with the 

 individual, or do they become in his descendants a new, an ac- 

 quired character ? * The brain, for example, like every other organ, 

 is developed by exercise. If this increase, whether of size or 

 of energy, is transmissible, some important consequences for the 

 mental faculties must be the result ; progress will then be deter- 

 mined, not only outwardly and traditionally, but inwardly and 

 organically. 



We will consider this question in the course of the work ; for 

 the present we consider only the physiological phenomena. 



Habit is defined to be an acquired disposition. We ask if any 

 purely individual habits are transmitted. Instances of this are cited. 

 Girou de Buzareingues observes that he had known a man who 

 had the habit, when in bed, of lying on his back and crossing the 

 right leg over the left. One of his daughters had the same habit 

 from birth; she constantly assumed that posture in the cradle, 

 notwithstanding the resistance offered by the napkins. * I know 

 many girls,' says he, 'who resemble their fathers, and who 

 have derived from them extraordinary habits, which cannot be 

 attributed either to imitation or to training, and boys who have 

 habits derived from their mothers. 1 But it is impossible to enter 

 upon any details on this subject.' Darwin notes the following 

 instance, which came under his own observation : a boy had the 

 singular habit, when pleased, of rapidly moving his fingers parallel 

 to each other; and when much excited, of raising both hands, 

 with the fingers still moving, to the sides of his face on a level with 

 the eyes; this boy, when almost an old man, could still hardly 

 resist this trick when much pleased, but, from its absurdity, con- 

 cealed it. He had eight children. Of these, a girl, when pleased, 

 at the age of four and a half years, moved her fingers in exactly 



1 De la Gen'eration, 282. 



