46o PRIMARY FACTORS OF ORGANIC EVOLUTION. 



than appears at first sight to belong to it. He shows^ 

 that the ancestors of the individuals of a given species 

 are in greater or less degree identical persons, and 

 that they are on this account less numerous than has 

 been sometimes assumed. Thus, if the population of 

 a given district had for ten generations married first 

 cousins, the total ancestry of each person for that 

 period would number only thirty-eight persons. If, 

 on the contrary, all the ancestors of each person had 

 been distinct individuals, the total number of ances- 

 tors in ten generations would be two thousand and 

 forty-six persons. An investigation into the ancestry 

 of three persons, not nearly related, living on an island 

 on the Atlantic coast where the records are complete 

 for seven and eight generations, shows that the ances- 

 try of each of the three averages only three hundred 

 and eighty-two persons. That this consideration is of 

 even greater importance in estimating the ancestry of 

 the lower animals than in man, is evident from the 

 fact that no consideration of kinship modifies their re- 

 productive habits. 



The fact that mutilations are not generally inherited 

 is cited as evidence against the inheritance of acquired 

 characters. A particular mutilation, however, as al- 

 ready remarked, rarely happens more than once or 

 twice in the lifetime of a single individual; in fact its 

 occurrence more than once is, in many cases, as in 

 amputations, impossible. Such sporadic events must 

 necessarily have little influence as stimuli to the organ- 

 ism, in comparison with the habitual movements of ani- 

 mals, or the continued exposure to especial physical 

 conditions, as is experienced by both plants and ani- 

 mals, and are not worth considering in this connection. 



1 Science^ 1895, February, p. I2l. 



