1879. | Ultimate Physical Unit of Living Matter. 13 
recorded instances in the human family of the effect of the 
so-called pre-natal influences would justify such an inference. 
The phenomena of development presented by the embryologi- 
cal history of an organism, are serially or successively related to 
series of ancestral forms in a way which shows that the most 
remote ancestor was indubitably unicellular, for all beings com- 
mence their embryonic history as a one-celled egg, or as an egg- 
cell fused with one or more unicellular spermatozooids. To this 
law no exception has ever been discovered. It passes at first by 
a process, then by processes, as complication is established by the 
‘former; not by leaps, but from one stage to the next higher, and 
so on in an absolutely continuous manner, so that it is impossible 
to mark the transitions, so that absolute continuity becomes a 
fundamental characteristic of the process of development. 
It has also been noted that these successive stages, or a part of 
them, often represent, perhaps always within the limits of groups, 
a sort of recapitulation or successive shadowing forth, sometimes 
faintly, sometimes strongly, of the forms which appear to repre- 
sent the phases through which the organism has passed in attain- 
ing its present form and structure. The process of development. 
accordingly shows in a pronounced, or may be dim way, the 
types which have successively formed the starting points of its 
development in past time. A phylum or branch from the tree of 
life or chain of ancestors, is thus represented in its embryonic 
history. The being, in its evolution from the ovum, accordingly 
recapitulates the forms of its successively more and more com- 
plex, or more and more modified ancestral series—its palzon- 
tological history preserved in the rocks together with more or 
less note of its living cotemporary allies. The fossil forms of 
successive formations are frequently found to bear such a rela- 
tion to the developing embryo. The rock record linked with the 
now living one is said to be the phylogenetic history, that is, it 
unfolds the history of the fy/a, or branches of the tree of life. 
The history of the being or ontological history, therefore, becomes 
a more or less distinct record of the phylogenetic. In a word, 
Ontogeny, or the development of individual beings, is an epitome 
of the Phylogeny or phylogenesis of the race to which they 
belong. . - 
This doctrine and its modifications is the motive force of 
modern Biology. Upon this ground, Laplace, Lamarck, Wolf, 
