previously. He considers the matter from the point of view of development,
and after indicating the probability that hormones are given off by all
the tissues of the body, gives instances of organs being formed in
regeneration (eye of shrimp) or larvae (common sea-urchin) as the result
of the presence of neighbouring organs, an influence which he thinks can
only be due to a hormone given off by the organ already present. He then
states that Professor Langley had pointed out to him in correspondence
that if an animal changes its structure in response to a changed
environment, the hormones produced by the altered organs will be changed.
The altered hormones will circulate in the blood and bathe the growing and
maturing genital cells. Sooner or later, he assumes, some of these
hormones may become incorporated in the nuclear matter of the genital
cells, and when these cells develop into embryos the hormones will be set
free at the corresponding period of development at which they were
originally formed, and reinforce the action of the environment. In this
way MacBride attempts to explain recapitulation in development and the
tendency to precocity in the development of ancestral structures. His idea
that the hormones act by 'incorporation' in the genital cells is different
from that of stimulation of determinants put forward by myself and others,
but it is surprising that he should refer to unpublished suggestions of
Professor Langley, and not to the publications of authors who had
previously discussed the possible action of hormones in connexion with the
heredity of somatic modifications.

Dr. J. G. Adami in 1918 published the Croonian Lectures, delivered by him
in 1917 under the title 'Adaptation and Disease,' together with reprints
of previous papers, in a volume entitled _Medical Contributions to the
Study of Evolution_. In this work (footnote, p. 71) the author claims
that he preceded Professor Yves Delage by some two years in offering a
physico-chemical hypothesis in place of determinants, and also asserts