3 
a 
200 EVOLUTION IN BIOLOGY VI 
still less does it consist of the “molecules or- 
ganiques ” of Buffon. The new material is, in great 
measure, not only absorbed but assimilated, so 
that it becomes part and parcel of the molecular 
structure of the living body into which it enters. 
And, so far from the fully developed organism 
being simply the germ plus the nutriment which 
it has absorbed, it is probable that the adult con- 
tains neither in form, nor in substance, more than 
an inappreciable fraction of the constituents of 
the germ, and that it is almost, if not wholly, 
made up of assimilated and metamorphosed 
nutriment. In the great majority of cases, at 
any rate, the full-grown organism becomes what 
it is by the absorption of not-living matter, and 
its conversion into living matter of a specific type. 
As Harvey says (Ex. 45), all parts of the body 
are nourished “ab eodem succo alibili, aliter 
aliterque cambiato,” “ut plantee omnes ex eodem 
communi nutrimento (sive rore seu terre 
humore).” 
Tn all animals and plants above the lowest the 
germ is a nucleated cell, using that term in its 
broadest sense ; and the first step in the process — 
of the evolution of the individual is the division 
of this cell into two or more portions, The pro-- 
cess of division is repeated, until the organism, 
from being unicellular, becomes multicellular.. 
The single cell becomes a cell-ageregate ; and it 
is to the growth and metamorphosis of the cells 
