1906 ] 



BROCJKS— HEREDITY AND VARIATION. 71 



relatives more than it resembles anything else in nature, it is never 

 identical with them. We say, in our careless way, that organisms 

 exhibit specific identity behind or in spite of their individual diver- 

 sity, when all we mean is that, while they resemble their parents, 

 they are never identical with them. This diversity in unity is com- 

 mon to all natural objects, but it is most impressive in familiar living 

 beings, in our friends and acquaintances, in our dogs and horses, 

 and in the plants that we tend with our own hands. We may think 

 of the casual stranger in the crowded street, or the unknown citizen 

 of Timbuctoo, or the stalks in the cornfield that we pass in the train, 

 as representatives of species and nothing more, but all the living 

 beings we know practically we know as individual members of their 

 kind. 



If we are permitted to reason from the living beings we know 

 best to those that concern us less, we must conclude that every living 

 being is a unique member of its kind. It is more like its kind than 

 like anything else in nature, but it is unique for there is nothing else 

 in nature just like it. Reproduction is not the generation of like 

 by like in any literal or mathematical sense. It is, rather, the genera- 

 tion of unique beings that are, on the average, more like their allies 

 than they are like anything else in nature. We may for our. own 

 purposes, and in our minds, consider their kinship apart from their 

 individuality, but this does not show that their kinship is separated 

 from their individuality in fact. Living beings do not exhibit unity 

 and diversity, but unity in diversity. These are not two facts but 

 one. The delight of intimate acquaintance with animals is due to 

 the inseparableness of their specific unity from their individuality, 

 and our attempts to separate in our minds what is not separable in 

 fact lead us to two narrow and imperfect views of the facts, two 

 crude and unfinished mental concepts, neither of which corresponds 

 to anything in nature. 



All this is familiar, but I ask you to reflect upon it, to decide for 

 yourselves whether it does not mean that inheritance or resemblance 

 to ancestors, and variation or difference from ancestors, are only 

 imperfect mental concepts ; crude ideas, and not facts ; whether the 

 fact is not the individuality in kinship of living beings. Each of you 

 must answer this simple question for himself. I cannot regard them 



