insight into the nature of the hereditary process.

While Galton was working in England the German zoologist August Weismann
was elaborating the complicated {14} theory of heredity which eventually
appeared in his work on _The Germplasm_ (1885), a book which will be
remembered for one notable contribution to the subject. Until the
publication of Weismann's work it had been generally accepted that the
modifications brought about in the individual during its lifetime, through
the varying conditions of nutrition and environment, could be transmitted
to the offspring. In this biologists were but following Darwin, who held
that the changes in the parent resulting from increased use or disuse of
any part or organ were passed on to the children. Weismann's theory
involved the conception of a sharp cleavage between the general body
tissues or somatoplasm and the reproductive glands or germplasm. The
individual was merely a carrier for the essential germplasm whose
properties had been determined long before he was capable of leading a
separate existence. As this conception ran counter to the possibility of
the inheritance of "acquired characters," Weismann challenged the evidence
upon which it rested and showed that it broke down wherever it was
critically examined. By thus compelling biologists to revise their ideas as
to the inherited effects of use and disuse, Weismann rendered a valuable
service to the study of genetics and did much to clear the way for
subsequent research.

A further important step was taken in 1895, when Bateson once more drew
attention to the problem of the origin {15} of species, and questioned
whether the accepted ideas of variation and heredity were after all in
consonance with the facts. Speaking generally, species do not grade
gradually from one to the other, but the differences between them are sharp
and specific. Whence comes this prevalence of discontinuity if the process
by which they have arisen is one of accumulation of minute and almost
imperceptible differences? Why are not intermediates of all sorts more
abundantly produced in nature than is actually known to be the case?
Bateson saw that if we are ever to answer this question we must have more
definite knowledge of the nature of variation and of the nature of the
hereditary process by which these variations are transmitted. And the best
way to obtain that knowledge was to let the dead alone and to return to the
study of the living. It was t