DARWIN'S THEORY UNSHAKEN 29 



This is called "variation." It is familiar to us all in the 

 case of the organism which we know best, and observe 

 most closely, namely, man. It is also a matter of common 

 observation in the case of dogs, cats, horses, and other 

 domesticated animals. Many of these " variations " are 

 exhibited in points of size, proportion, and colour, which 

 are easily noted at once by the eye. But " variation " is 

 really a deep-seated thing, and depends on causes which 

 lie below the surface. We know that the offspring of 

 men and of animals and of plants, give evidence of 

 variations in what we call constitution, tendency, tem- 

 perament, aptitude, strength, and that the colour, and 

 even size of this or that part, are really only indications 

 of a deep-seated difference in the living chemistry, the 

 forces of nutrition and growth which reside in the living 

 substance. The fact that many thousands of a species 

 may be born and only a few survive, means therefore 

 that many thousand varieties, often varieties not readily 

 measured by the eye, are produced in each generation, 

 from which a few individuals are in some way " selected " 

 for survival. 



(3) The third great fact is that though there is varia- 

 tion, amongst all the offspring in each generation, there 

 is also a continual and definite inheritance by offspring of 

 the qualities and structure of their parents to a degree 

 which altogether preponderates over the variations. To 

 put it in another way, we all know that every parental 

 organism transmits to its young not only the qualities and 

 structure of the species, or of the race, or of the family, 

 but also transmits its own peculiarities or variations in 

 which it departed from its parents, and from its brothers 

 and sisters. This is best illustrated by our daily ex- 

 perience of human families. 



These facts being admitted, and abundantly illustrated 

 and traced in detail by years of observation and experi- 



