We are told the genius comes as a brain-variation; and between the physical heredity which produces him and the social heredity which sets the tradition of his time there is no connection.
But this is not tenable, as we have reason to think, from the interaction which actually takes place between physical and social heredity.

To be sure, the heredity of the individual is a physiological matter, in the sense that the son must inherit from his parents and their ancestors alone.

But granted that two certain parents are his parents, we may ask how these two certain parents came to be his parents.

How did his father come to marry his mother, and the reverse?
This is distinctly a social question; and to its solution all the currents of social influence and suggestion contribute.

Who is free from social considerations in selecting his wife?
Does the coachman have an equal chance to get the heiress, or the blacksmith the clergyman's daughter?
Do we find inroads made in Newport society by the ranchman and the dry-goods clerk?
And are not the inroads which we do find, the inroads made by the counts and the marquises, due to influences which are quite social and psychological?
Again, on the other hand, what leads the count and the marquis, to lay their titles at Newport doors, while the ranchman and the dry-goods clerk keep away, but the ability of both these types of suitors to estimate their chances just on social and psychological grounds?
Novelists have rung the changes on this intrusion of social influences into the course of physical heredity.