TWINS AND HEREDITY 487 



Now scientists cannot cold-bloodedly separate identical twins in 

 infancy and rear the two under radically different environments, but 

 fortunately this very thing has sometimes been done for them without 

 their knowledge. When by a stroke of good fortune we are able to 

 locate such cases, we have before us a scientific experiment completed 

 and only needing to be studied. During the last few years we have 

 completed the study of five such cases. A brief account of these five 

 cases, (one studied by Muller and five by Newman) may interest the 

 reader: 



Muller studied a pair of twin sisters, left orphans and separated 

 at two weeks. They did not meet until they were eighteen years old. 



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They lived under somewhat similar social conditions, in northwestern 

 mining and ranch country, but there were marked differences in their 

 educational and social experiences. Physically, although entirely sep- 

 arated from infancy to adulthood, they were as identical as are iden- 

 tical twins reared together. Their heights, weights, features, teeth 

 and finger nails, eye-color, hair-color, glove size, blood group, etc., 

 were indistinguishably similar. In addition, both were left-handed, 

 both had the same peculiar prominences on the ankles, and both had a 

 droop of the mouth on the left side. Both had had two or three at- 

 tacks of tuberculosis almost simultaneously. Intelligence tests showed 

 them to be both very bright, and their scores were as similar as those 

 commonly made by the same individual taking the tests twice over. 

 In the temperament and emotional tests, on the other hand, they 

 showed a very wide divergence, as great or greater than those be- 

 tween two individuals taken at random. In this case the environ- 

 mental differences had left the physical and intellectual characters 

 unmodified, but had produced a profound effect on the emotional 

 nature of the twins. 



Newman's first case consisted of a pair of twin sisters separated at 

 eighteen months. One was taken to Ontario, and the other remained 

 in London, England, where they were born. After seventeen years of 

 complete separation, the English twin joined her sister in Canada, 

 where they now live in a pleasant medium-sized town. Their environ- 

 ments were very different during the period of separation, as different 

 as one- is ever likely to find in cases of separated identical twins. 

 One was reared in a congested district of London and passed the trying 

 period of the war there; the other lived under good circumstances in a 

 suburban town in Ontario, and did not feel the pressure of war con- 

 ditions. Their educational careers were equal in amount and kind. 



