rk out in detail the unity of plan underlying the diversity of forms,
to disentangle the constant in animal form and distinguish from it the
accessory and adaptive. The main principle upon which this work was
based was the principle of connections, so clearly stated by Geoffroy.
The principle of connections served as a guide in the search for the
archetype, and this search was prosecuted in two directions--first, by
the comparison of adult structure; and second, by the comparative study
of developing embryos. It was found that the archetype was shown most
clearly by the early embryo, and this embryological archetype came to be
preferred before the archetype of comparative anatomy. It became
apparent also that the parts first formed (germ-layers) were of primary
importance for the establishing of homologies.

While practically all morphologists were agreed as to the main
principles of their science, they yet showed, as regards their general
attitude to the problems of form, a fairly definite division into two
groups, of which one laid stress upon the intimate relation existing
between form and function, while the other disregarded function
completely, and sought to build up a "pure" or abstract morphology. In
opposition to both groups, in opposition really to morphology
altogether, a movement had gained strength which tended towards the
analysis and disintegration of the organism. This movement took its
origin in the current materialism of the day, and found expression
particularly in the cell-theory and in materialistic physiology.

The separation between morphology as the science of form and physiology
as the science of the physics and chemistry of the living body had by
Darwin's day become well-nigh absolute.

The morphology of the 'fifties lent itself readily to evolutionary
interpretation. Darwin found it easy to give a formal solution of all
the main problems which pre-evolutionary morphology had set--he was able
to interpret the natural system of classification as being in reality
genealogical, systematic relationship as being really
blood-relationship; he was able to interpret homology and analogy in
terms of heredity and adaptation; he was able to explain the unity of
plan by descent from a common ancestor, and for the concept of
"archetype" to substitute that of "ancestral form."

The current morphology, Darwin found, could be taken over, lock, stock
and barrel, to the evolutionary camp.

In what follows w