Life, as was said in the first chapter, is something unique, with the unique property of being able to evolve.

As life evolves, that is to say changes, by being handed on from certain forms to certain other forms, a partial rigidity marks the process together with a partial plasticity.

There is a stiffening, so to speak, that keeps the life-force up to a point true to its old direction; though, short of that limit, it is free to take a new line of its own.

Race, then, stands for the stiffening in the evolutionary process.

Just up to what point it goes in any given case we probably can never quite tell.