VARIATION AND HEREDITY IN TWINS 167 



has just appeared in which a detailed comparison of the 

 convolutional pattern of the brains of a pair of stillborn, 

 full-term, Belgian war babies. These were adjudged, 

 and probably correctly, to be "identical" or mono- 

 zygotic twins, although there appear to be marked dif- 

 ferences in size, weight, facial and cranial indices, size 

 of brain and of head. "The boy called A has a more 

 receding forehead; the nose is more turned up; the 

 distance between the root of the nose and the superior 

 border of the upper lip smaller (6.5 mm. v. 8. mm.), 

 hence the mouth remains open. The chin is more 

 receding. The ear of A is closer to the head, has very 

 little enrolment of the border, and its lobule is adherent, 

 while the second boy's ear is more unfolded and graceful." 

 Although in these and other respects the twins are 

 quite strikingly different, they are ahke in eyes, in Hnes 

 and furrows of the hands, and in other inherited char- 

 acters. The author concludes "that the male twins 

 under examination are very similar to each other and 

 also to their mother. No essential differences were to 

 be found." 



The description of the brains of the twins is very 

 detailed and technical, but we may accept the author's 

 conclusion that, although the brain of twin B is larger 

 and somewhat more advanced in structure than that 

 of twin A, they are strikingly similar. My own opinion 

 as to the other differences pointed out by Sano is that 

 they too are to be interpreted as the result of a difference 

 in the degree of maturity of the two twins, B being 

 distinctly in advance of A. It will be recalled that 

 armadillo quadruplets in advanced pregnancy show 

 equally striking differences in developmental age. 



