tem of organisms (in harmony with
the principles of Lamarck and Darwin) in the form of a hypothetical
pedigree, and was provisionally set forth in eight genealogical tables.

In the nineteenth chapter of the "Generelle Morphologie"--a part of
which has been republished, without any alteration, after a lapse of
forty years--I made a critical study of Lamarck's theory of descent and
of Darwin's theory of selection, and endeavoured to bring the complex
phenomena of heredity and adaptation under definite laws for the first
time. Heredity I divided into conservative and progressive: adaptation
into indirect (or potential) and direct (or actual). I then found
it possible to give some explanation of the correlation of the two
physiological functions in the struggle for life (selection), and to
indicate the important laws of divergence (or differentiation) and
complexity (or division of labour), which are the direct and inevitable
outcome of selection. Finally, I marked off dysteleology as the science
of the aimless (vestigial, abortive, atrophied, and useless) organs
and parts of the body. In all this I worked from a strictly monistic
standpoint, and sought to explain all biological phenomena on the
mechanical and naturalistic lines that had long been recognised in the
study of inorganic nature. Then (1866), as now, being convinced of the
unity of nature, the fundamental identity of the agencies at work in the
inorganic and the organic worlds, I discarded vitalism, teleology, and
all hypotheses of a mystic character.

It was clear from the first that it was essential, in the monistic
conception of evolution, to distinguish between the laws of conservative
and progressive heredity. Conservative heredity maintains from
generation to generation the enduring characters of the species. Each
organism transmits to its descendants a part of the morphological
and physiological qualities that it has received from its parents and
ancestors. On the other hand, progressive heredity brings new characters
to the species--characters that were not found in preceding generations.
Each organism may transmit to its offspring a part of the morphological
and physiological features that it has itself acquired, by adaptation,
in the course of its individual career, through the use or disuse of
particular organs, the influence of environment, climate, nutrition,
etc. At that time I gave the name of "progressive heredity" to
this inheritance of acquir