Chap. XIV. SUMMAKY. 57 



Finally, from the numerous races of cultivated plants and 

 domestic animals, in which the seeds or eggs, the yoiing or 

 old, differ from one another and from those of the parent- 

 si^ecies : — from the cases in which new characters have ap- 

 peared at a particular period, and afterwards been inherited 

 at the same period ; — and from what we know with respect 

 to disease, we must believe in the truth of the great principle 

 of inheritance at corresponding periods of life. 



Summary of the three preceding Chapters. — Strong as is the 

 force of inheritance, it allows the incessant appearance of new 

 characters. These, whether beneficial or injurious, — of the 

 most trifling importance, such as a shade of colour in a flower, 

 a coloured lock of hair, or a mere gesture, — or of the highest 

 importance, as when affecting the brain, or an organ so perfect 

 and complex as the eye,— or of so grave a nature as to deserve 

 to be called a monstrosity, — or so peculiar as not to occur 

 normally in any member of the same natural class, — are often 

 inherited by man, by the lower animals, and plants. In 

 numberless cases it suffices for the inheritance of a pecu- 

 liarity that one parent alone should be thus characterised. 

 Inequalities in the two sides of the body, though opposed to 

 the law of symmetr}^, may be transmitted. 'J here is ample 

 evidence that the effects of mutilations and of accidents, es- 

 pecially or perhaps exclusively when followed by disease, are 

 occasionally inherited. There can be no doubt that the evil 

 effects of the long-continued exposure of the parent to in- 

 jurious conditions are sometimes transmitted to the offspring. 

 So it is, as we shall see in a future chapter, with the effects 

 of the use and disuse of parts, and of mental habits. Periodi- 

 cal habits are likewise transmitted, but generally, as it would 

 appear, with little force. 



Hence we are led to look at inheiitance as the rule, and 

 non-inheritance as the anomaly. But this power often ap- 

 pears to us in our ignorance to act capriciously, transmitting 

 a character with inexplicable strength or feebleness. The 

 yerj same peculiarity, as the weeping habit of trees, silky 

 feathers, d'c, may be inherited either firmly or not at all by 

 different members of the same group, and even by different 



