THE PROBLEMS ILLUSTRATED 19 



A pair of blue Andalusian fowls of selected breed have chickens. 

 But only about half of these are " blue," the rest are blacks or 

 splashed whites. Why is this ? The blacks inbred produce 

 only blacks, the splashed whites produce splashed whites or 

 whites, but if the blacks and splashed whites are paired the 

 progeny is altogether " blue." Why is this ? 



We read of a mare which, after bearing a foal to a quagga, 

 bore a zebra-striped foal to a horse. Breeders of dogs say that 

 a thoroughbred bitch is spoilt for true breeding if she has once 

 been crossed by a mongrel. Is it possible that a father can 

 influence the subsequent offspring of the same mother by a 

 different father ? This is a problem partly in scientific criticism 

 of evidence, but it raises interesting questions regarding the 

 physiology of reproduction and regarding the hereditary relation. 



In the sixteenth century Montaigne was puzzled by the fact 

 that, at the age of forty-five, he developed, just like his father, 

 a stone in the bladder. The puzzle of the supposed legacy had 

 its fine point in the fact that his father did not develop his stone 

 till he was sixty-seven years of age, or twenty-five years after 

 Montaigne was born ! It is possible that there was here an 

 interesting problem in inheritance ; but the likelihood is that it 

 merely illustrated the commonest of phenomena, the inheritance 

 of a constitutional tendency and the repetition of more or less 

 similar habits of life. 



Far too much has been made of homochronous heredity ! — 

 i.e. of the fact that some item in the inheritance may be ex- 

 pressed in the offspring at the same age as in the parents. Thus 

 two brothers, their father, and their maternal grandfather be- 

 came deaf at the age of forty ; blindness occurred in a father 

 and in his four children at the age of twenty-one. But if the 

 constitutions are similar and if the conditions of life are similar, 

 it is not surprising that the expression of an item in the con- 

 stitution should reach its climax at the same age. 



A case is recorded of abnormalities in the fingers traceable 



