Chap. XII. INHERITANCE. 449 



— that their production stands in hardly closer relation to the 

 conditions of life than does life itself. If this be so, and the 

 occurrence of the same unusual character in the child and 

 parent cannot be attributed to both having been exposed to 

 the same unusual conditions, then the following problem is 

 worth consideration, as showing that the result cannot be 

 due, as some authors have supposed, to mere coincidence, but 

 must be consequent on the members of the same family 

 inheriting something in common in their constitution. Let 

 it be assumed that, in a large population, a particular affec- 

 tion occurs on an average in one out of a million, so that the 

 a priori chance that an individual taken at random will be 

 so affected is only one in a million. Let the population 

 consist of sixty millions, composed, we will assume, of ten 

 million families, each containing six members. On these 

 data, Professor Stokes has calculated for me that the odds 

 will be no less than 8333 millions to 1 that in the ten million 

 families there will not be even a single family in which one 

 parent and two children will be affected by the peculiarity 

 in question. But numerous instances could be given, in 

 which several children have been affected by the same rare 

 peculiarity with one of their parents ; and in this case, more 

 especially if the grandchildren be included in the calculation, 

 the odds against mere coincidence become something prodi- 

 gious, almost beyond enumeration. 



In some respects the evidence of inheritance is more 

 striking when we consider the reappearance of trifling pecu- 

 liarities. Dr. Hodgkin formerly told me of an English family 

 in which, for many generations, some members had a single 

 lock differently coloured from the rest of the hair. I knew 

 an Irish gentleman, who, on the right side of his head, had a 

 small white lock in the midst of his dark hair : he assured 

 me that his grandmother had a similar lock on the same side, 

 and his mother on the opposite side. But it is superfluous to 

 give instances ; every shade of expression, which may often 

 be seen alike in parents and children, tells the same story. 

 On what a curious combination of corporeal structure, mental 

 character, and training, handwriting depends ! yet every one 

 must have noted the occasional close similarity of the hand- 



