400 



The Journal of Heredity 



still more rarely, what are otherwise 

 similar twins may be characterized by 

 one or two points of difference. As an 

 illustration of the latter class, there may 

 be mentioned a pair which in a baby 

 show were scored as identical except' 

 for the shape of the occipital region of 

 the head. 



Physiological Traits. — Such mani- 

 festations of the general make-up as 

 gait, sound of the voice, reaction to 

 foods, susceptibility to disease, all show 

 a distribution similar to that of the 

 purely physical traits. One pair of 

 twins state that bananas make them 

 "both very sick." Another pair have 

 no special aversion for any food but 

 tapioca. Still another pair agree in all 

 their likes and dislikes except for cante- 

 loupe. In other cases the lists of 

 preference-! differ very considerably. 



THE ""mirror image" OF EACH OTHER 



Perhaps the matter of right and left 

 handedness should not be passed over 

 in this connection. Rather a surprising 

 number of twin pairs seem to be com- 

 posed of one right and one left handed 

 individual. It has been suggested that 

 one twin is frequently the "mirror 

 image" of the other, left-handed and 

 with heart and other viscera reversed 

 in their symmetry. The responses to 

 the questionnaire do not show definitely 

 whether or not this condition, known to 

 anatomists as situs inversus, occurs in 

 any of these twins. Some persons be- 

 lieve that right or left handedness is an 

 acquired characteristic and not heredi- 

 tary. While this position probably can- 

 not be maintained, it may be of inter- 

 est to recad that twin babies generally 

 face each other in their beds, and if 

 care is not taken to change them about 

 frequently their heads become asymetri- 

 cal on opposite sides. This may possibly 

 affect the hemisphere of the brain dif- 

 ferently and certainly influences the 

 amount of use that is made of the left 

 hand in one infant and the right in the 

 other. 



Handwriting. — Each twin was asked 

 to copy a short sentence. The hand- 

 writing of the two members of a pair 



frequently showed great similarity and 

 in one case was virtually identical. In 

 other instances the differences in style 

 and other characteristics were very 

 noticeable. 



Mental Traits. — Much of the in- 

 formation received through the ques- 

 tionnaires concerned mental capacities, 

 intellectual tastes, and likes and dis- 

 likes. Without analyzing this data in 

 detail it may be stated thar ample evi- 

 dence is afforded that the same resem- 

 blances and differences obtain with 

 reference to mental traits as are found 

 for characteristics that are generally 

 thought of as more purely physical or 

 physiological. Over and over the two 

 twins of a pair enumerate virtually the 

 same list of preferences and aversions- 

 One pair of twin girls heartily dislike 

 mathematics, while another pair record 

 it as their favorite study. One twin 

 mentions that not only do she and her 

 sister commonly dream about the same 

 person at the same time but they dream 

 the same things about them. She states 

 that this happens even when they are 

 in different places. 



STRONGER AFFECTION 



Many twins state that their fondness 

 for each other far exceeds their liking 

 for other brothers and sisters. Both 

 men and women twins write that they 

 are always dissatisfied when separated 

 from their co-twins. "No one was ever 

 quite so entertaining to us as the other." 

 It is noticeable that twins who express 

 this sentiment are not only of the same 

 sex, but otherwise similar. 



On the other hand there are plenty 

 of twins who differ widely in their 

 tastes and capacities and who find their 

 co-twin no more congenial than their 

 other brothers and sisters, indeed some- 

 times less so. These are the "Jacobs 

 and Esaus," as a twin in an insane 

 asylum once explained to the writer. 



Summary. — Summarizing this very 

 sketchy review of the questionnaires, it 

 may be said that there is ample evidence 

 that the twins of certain pairs show 

 profound resemblances in both physical 

 and mental traits, while those of other 



