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5 modified around us to-day and find out what characters are transmissible. The nature and causes of Variation and of Heredity will thus in time come to be understood.

It is only within recent years that any attempt has been made to study variations systematically. Mr.Bateson's work, entitled, is an important contribution in this direction. He is not content with the knowledge that variability exists but seeks to find out by detailed investigations of particular cases what variations actually do occur in nature. He brings forward evidence to show that there are variations which cannot be arranged in a continuous series—that such variations are therefore discontinuous. This is not peculiar to any one kind of variation. This discontinuity of variation is something akin with polymorphism—in fact it may be regarded as one of the forms under which polymorphism may show itself. Darwin never contemplated the existence of polymorphism, except where the polymorphism is of some advantage. But the test of utility cannot be applied to explain the definiteness of structure which is so often seen. Differences appear often in the most trivial points. Darwin never entertained the idea that discontinuity could be a starting-point of species. He tended to regard variation as always slow and almost imperceptible: species arose by the natural selection of "numerous successive, slight favourable variations".