52 THE PHYSICAL BASIS OF INHERITANCE 



the complex product of ancestral lineage. We shall return to 

 the subject when we come to consider Galton's Law of Ancestral 

 Inheritance. 



Though a comparison with the inheritance of property is apt 

 to mislead, it may be of use to think for a moment of a youth 

 inheriting an estate, of which one might accurately say that it 

 had belonged in half to his father and in half to his mother. 

 Yet a genealogist with a full knowledge of the family might be 

 able to go further back, and might show, with even greater 

 accuracy, how this corner was due to a grandmother and that 

 to a great-grandfather. 



This conception is so fundamentally important that I cannot 

 refrain from quoting an illustration from Mr. Galton's Natural 

 Inheritance, which puts the matter very clearly. " Many of the 

 modern buildings in Italy are historically known to have been 

 built out of the pillaged structures of older days. Here we may 

 observe a column or a lintel serving the same purpose for a 

 second time, and perhaps bearing an inscription that testifies 

 to its origin ; while as to the other stones, though the mason may 

 have chipped them here and there and altered their shape a little, 



few if any came direct from the quarry This simile gives 



a rude though true idea of the exact meaning of Particulate 

 Inheritance — namely, that each piece of the new structure is 

 derived from a corresponding piece of some older one, as a lintel 

 was derived from a lintel, a column from a colimin, a piece of 

 wall from a piece of wall. , . . We appear to be severally built 

 up out of a host of minute particles of whose nature we know 

 nothing, any one of which may be derived from any one 

 progenitor, but which are usually transmitted in aggregates, con- 

 siderable groups being derived from the same progenitor. It 

 would seem that while the embryo is developing itself, the 

 particles more or less qualified for each post wait, as it were, in 

 competition to obtain it. Also that the particle that succeeds 

 must owe its success partly to accident of position and partly to 



