THE LAW OF ANCESTRAL HEREDITY 169 



upon the offspring, and this chance grows rapidly less as we go 

 backward, never, however, becoming zero ; so that it is possible 

 that resemblances to any ancestor, no matter how far removed, 

 may crop out in individual cases from time to time, giving 

 strange but not unaccountable cases of reversion. These are ex- 

 tremely noticeable, first, from their variety ; and second, from the 

 fact that complete ignorance generally surrounds all ancestry 

 more than a generation or two back. What chance is there, for 

 example, for knowing much about the separate characters of 

 each of the thirty individuals involved in the first four genera- 

 tions only ? The next generation backward would add thirty-two 

 more, showing how rapidly the transmission becomes compli- 

 cated, particularly when we remember that all the ancestry has 

 contributed to the individual. 



The individual a composite. This makes it look as if the 

 individual were pretty well distributed among his ancestry from 

 his parents backward, and that is exactly the condition of matters. 

 The individual is a kind of mosaic, taking a portion (on the 

 average one half) of his resemblances from his parents, others 

 from his grandparents, and still others from earlier ancestors, 

 even to the remote past. 



At first thought this may seem impossible, but upon careful 

 research we find that racial characters are but loosely held to- 

 gether, 1 and it is only upon reflection that we realize the extent 

 to which combinations and recombinations take place and how 

 resemblances come and go in a long line of ancestry. 



In this way an individual may seem in some particular to re- 

 semble, we will say, the paternal grandsire, whereas the actual 

 resemblance is not only to him but to perhaps a score or more 

 of similar ancestors still further back and long forgotten, but 

 whose blood lines combined with and intensifying those of 



1 Shown by the fact that the M correlation " or bond that compels characters 

 to move together is very low, seldom as much as 50 per cent, so that almost 

 literally it is a free-for-all contest when matters of hereditary resemblances 

 are being determined. For a full discussion of Correlation, see " Principles of 

 Breeding," chap. xiii. 



