What is Heredity? 



and mental activities of animals. We do not under- 

 stand the machinery, but we find that it is there, and we 

 can interrupt its work by obstructing or injuring it. 

 Our wonder is not a feeling of mystery, a sense that the 

 phenomena transcend knowledge ; it is due to a percep- 

 tion of the amount of knowledge required. We regard 

 an adult animal with feelings similar to those with 

 which an intelligent savage might regard a telephone or 

 a steamboat. 



A dog, with all the powers and faculties which enable 

 him to fill his place as man's companion, is a wonder al- 

 most beyond our powers of expression; but we find in his 

 body the machinery of muscles and veins, digestive, 

 respiratory, and circulatory organs, eyes, ears, etc., 

 which adapts him to his place; and study has taught us 

 enough about the action of this machinery to assure us 

 that greater knowledge would show us, in the structure 

 of the dog, an explanation of all that fits the dog for his 

 life; an explanation as satisfactory as that which a savage 

 might reach, in the case of the steamboat, by studying 

 its anatomy. 



Let our savage find, however, while studying an iron 

 steamboat that small masses of iron, without structure, so 

 far as the means at his command allow him to examine 

 and decide, are from time to time broken off and thrown 

 overboard, and that each of these contains in itself the 

 power to build up all the machinery and appliances of a 

 perfect steamboat. The wonderful thing now is not the 

 adaptation of wonderful machinery to produce wonderful 

 results, but the production of wonderful results without 

 any discoverable mechanism; and this is, in outline, the 

 problem which is brought before the mind of the natu- 

 ralist by the word heredity. 



Every one knows that each dog exists at some time 



