STRIKINGLY ALIKE IN OLD AGE 



When these pictures were taken in 1915 these twins were about eighty years old. They had 

 never been more than 10 months away from the village of Bethal, Maine, in all their lives. 

 They invariably went for a walk every afternoon at al)Out 4 o'clock, always accompanied by 

 the two white cats. (Fig. 23.) 



The great lesson derived from the 

 records of identical twins is that the or- 

 dinary differences within the uterus of 

 tlie mother and the ordinary differences 

 within the home Hfe and school life 

 and even adult life are not of sufficient 

 force to modify greatly the control of 

 the chromosomes. 



The non-identical or "fraternal"' 

 twins have the same chance to become 

 similar through environmental action as 

 the "identical," yet they are not so 

 moulded. Photographs show this in 

 the most obvious manner, and, if as 

 appears from the records of the ques- 

 tionnaires, the resemblances are no 

 greater in pliysical than in mental 



aspects, then the far-reaching inference 

 is forced upon us that even mental and 

 moral differences are controlled by 

 forces lying in the primary chromo- 

 somes. 



This does not mean that great 

 changes in the environment may not 

 cause considerable modification in the 

 individual ; but the point is that great 

 changes are not tisual. The very fact 

 that they are great is associated with 

 their scarcity, and under usual condi- 

 tions of life the physical and mental 

 dift'erences that we commonly observe 

 among our fellow-beings are really dtie 

 to differences traceable in the chromo- 

 somes tliemselves. 



425 



