a 
VITAL PRINCIPLE. 9 
these operations, we can predict with certainty, that from 
the small egg of the butterfly shall burst forth the destruc- 
tive caterpillar; that this, in its turn, shall appear a dor- 
mant pupa, and, in due time, assume the elegant form and 
variegated colours of the sportive imago. 
C. Structure.—This same power, which is restricted as 
to the form and size of the being it is destined to con- 
struct, is likewise regulated with regard to structure. Thus 
the germ of the palm-tree is destined to produce a stem, 
which shall increase by the addition of matter on its cen- 
tral aspect, and the fibres or nerves of whose leaves shall 
be arranged nearly in straight lines. The germ of the 
oak, on the other hand, is destined to construct a trunk 
which shall increase in size by the addition of layers to 
its circumference, and the nerves of whose leaves shall 
exhibit a reticular arrangement. The germs of animals, 
in like manner, are regulated by similar laws. Individuals 
of the same species are constructed according to the same 
plan, and are furnished with the same members and organs, 
although they differ more or less from those of every other 
species. In short, in each species there is a power capable 
of producing all the modes of that species, and incapable 
of producing those of any other. 
D. Composition—The power which organized bodies 
thus possess of attracting towards them the particles of 
inorganic matter, is not exercised indiscriminately. There 
is a principle of selection, which displays itself in the pro- 
duction of different substances from the same materials. 
The plants which grow on the same soil, which are nou- 
rished by the same water, and invigorated by the same 
temperature, select from that soil the particles suited to 
their nourishment. But all do not select the same par- 
ticles. The wheat, barley and oats, draw towards them 
the particles adapted to construct their respective systems. 
