The Evolution of Man, vol 1 | Page 8

given, as most of my readers have
not studied anatomy, and are not likely to be entrusted with the care of
the adult organism. I must content myself with giving some parts of the
subject only in general outline, and must not enter upon all the
marvellous, but very intricate and not easily described, details that are
found in the story of the development of the human frame. To
understand these fully a knowledge of anatomy is needed. I will
endeavour to be as plain as possible in dealing with this branch of
science. Indeed, a sufficient general idea of the course of the embryonic
development of man can be obtained without going too closely into the
anatomic details. I trust we may be able to arouse the same interest in
this delicate field of inquiry as has been excited already in other
branches of science; though we shall meet more obstacles here than
elsewhere.
The story of the evolution of man, as it has hitherto been expounded to
medical students, has usually been confined to embryology--more
correctly, ontogeny--or the science of the development of the individual
human organism. But this is really only the first part of our task, the
first half of the story of the evolution of man in that wider sense in
which we understand it here. We must add as the second half--as
another and not less important and interesting branch of the science of
the evolution of the human stem--phylogeny: this may be described as
the science of the evolution of the various animal forms from which the
human organism has been developed in the course of countless ages.
Everybody now knows of the great scientific activity that was

occasioned by the publication of Darwin's Origin of Species in 1859.
The chief direct consequence of this publication was to provoke a fresh
inquiry into the origin of the human race, and this has proved beyond
question our gradual evolution from the lower species. We give the
name of "Phylogeny" to the science which describes this ascent of man
from the lower ranks of the animal world. The chief source that it
draws upon for facts is "Ontogeny," or embryology, the science of the
development of the individual organism. Moreover, it derives a good
deal of support from paleontology, or the science of fossil remains, and
even more from comparative anatomy, or morphology.
These two branches of our science--on the one side ontogeny or
embryology, and on the other phylogeny, or the science of
race-evolution--are most vitally connected. The one cannot be
understood without the other. It is only when the two branches fully
co-operate and supplement each other that "Biogeny" (or the science of
the genesis of life in the widest sense) attains to the rank of a
philosophic science. The connection between them is not external and
superficial, but profound, intrinsic, and causal. This is a discovery
made by recent research, and it is most clearly and correctly expressed
in the comprehensive law which I have called "the fundamental law of
organic evolution," or "the fundamental law of biogeny." This general
law, to which we shall find ourselves constantly recurring, and on the
recognition of which depends one's whole insight into the story of
evolution, may be briefly expressed in the phrase: "The history of the
foetus is a recapitulation of the history of the race"; or, in other words,
"Ontogeny is a recapitulation of phylogeny." It may be more fully
stated as follows: The series of forms through which the individual
organism passes during its development from the ovum to the complete
bodily structure is a brief, condensed repetition of the long series of
forms which the animal ancestors of the said organism, or the ancestral
forms of the species, have passed through from the earliest period of
organic life down to the present day.
The causal character of the relation which connects embryology with
stem-history is due to the action of heredity and adaptation. When we
have rightly understood these, and recognised their great importance in
the formation of organisms, we can go a step further and say:
Phylogenesis is the mechanical cause of ontogenesis.* (* The term

"genesis," which occurs throughout, means, of course, "birth" or origin.
From this we get: Biogeny = the origin of life (bios); Anthropogeny =
the origin of man (anthropos); Ontogeny = the origin of the individual
(on); Phylogeny = the origin of the species (phulon); and so on. In each
case the term may refer to the process itself, or to the science
describing the process.--Translator.) In other words, the development of
the stem, or race, is, in accordance with the laws of heredity and
adaptation, the cause of all the changes which appear in a condensed
form in the evolution of the foetus.
The chain