The Making of Species 



considerable part in the making of new species, 

 inasmuch as they may, so to speak, pave the way 

 for mutations. 



We are now in a position to consider the 

 exceedingly difficult question of inheritance. We 

 know that offspring tend to resemble their 

 parents, but that they are always a little different 

 both from either parent and from one another. 

 How are we to account for these phenomena? 

 What are the laws of inheritance, whereby a 

 child tends to inherit the peculiarities of its 

 parents, and what are the causes of variation 

 which make children differ inter se and from 

 their parents ? 



Scores of theories of inheritance have been 

 advanced. It is scarcely exaggerating to assert 

 that almost every biologist who has paid much 

 attention to the subject has a theory of inherit- 

 ance which differs more or less greatly from the 

 theory held by any other biologist. 



As regards the phenomena of heredity we may 

 say Tot homines tot sententice. 



For this state of affairs there is a good and 

 sufficient reason. We are not yet in possession 

 of a sufficient number of facts to be in a position 

 to formulate a satisfactory theory of inheritance. 

 A complete theory of heredity must explain, 

 among other things, the following phenomena : 



i. Why creatures show a general resemblance 

 to their parents. 



