REPRODUCTION AND HEREDITY 321 



black, the first hybrid generation contains only blue birds, which 

 on continued breeding regularly split once more into blue, black, 

 and spotted. We have here doubtless a typical case of Mendelism 

 which may be compared to the behaviour of the two Mirabilis 

 Jalapa races. 



As early as 1895 Haacke reported that the crossing of the 

 spotted Japanese dancing mouse with our ordinary grey mouse 

 in the first generation produced only normal young. In sub- 

 sequent generations the remarkable abnormity reappeared in a 

 number of individuals in the definite proportion demanded by 

 the rule. 



Finally, let us consider two interesting instances taken from 

 human life. The first case was observed by Castle on the 

 marriage of a negro-albino with a normal negress, Here albinism 

 proved to be ' recessive.' More remarkable is the second case. 

 In the year 1710, in Brandon, in Suffolk, a child was born of 

 healthy parents, whose entire body, with the exception of the 

 face and inner hand and feet surfaces, began a few months after 

 birth to be covered with a black horny skin. All the numerous 

 brothers and sisters of this strange child, which appeared to feel 

 quite comfortable in its horny skin and possessed no other defects, 

 were normally formed. When the boy became a man he married 

 a young Irish woman, and all six children of this marriage 

 uniformly exhibited this characteristic of their father. With 

 remarkable tenacity the horny skin was transmitted from genera- 

 tion to generation, but of the three following generations only 

 a part of the descendants had this natural armour, while the 

 others were normal. A descendant of this strange race was the 

 1 porcupine man,' J. Lampert, made famous by the investiga- 

 tions of Tilesius and Darwin, who at the beginning of the last 

 century, in company with his similarly affected younger brother, 

 travelled through England, Germany and France, exhibiting 

 themselves for money. The seven sisters of these two brothers 

 had perfectly pure soft skins. In view of the small number of 

 descendants we are naturally unable to prove a complete agree- 

 ment with the figures which we should expect under the 

 Mendelian law, but we may, nevertheless, regard this case with 

 a high degree of probability as an instance of the 'rule of 

 prevalence.' The only unexplained feature in this case was that 

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