overlooking their essential
identity of structure. We have seen instances of this among Acalephs,
and it is still more apparent among trees which produce simultaneously
leaf and flower-buds, and even separate male and female flower-buds, as
is the case with our Hazels, Oaks, etc.

It is not, however, my purpose here to describe the various modes of
reproduction and multiplication among animals and plants, nor to discuss
the merits of the different opinions respecting their numeric increase,
according to which some persons hold that all types originated from a
few primitive individuals, while others believe that the very numbers
now in existence are part of the primitive plan, and essential to the
harmonious relations existing between the animal and vegetable world. I
would only attempt to show that in the plan of Creation the maintenance
of types has been secured through a variety of means, but under such
limitations, that, within a narrow range of individual differences, all
representatives of one kind of animals agree with one another, whether
derived from eggs, or produced by natural division, or by budding; and
that the constancy of these normal processes of reproduction, as well as
the uniformity of their results, precludes the idea that the specific
differences among animals have been produced by the very means that
secure their permanence of type. The statement itself implies a
contradiction, for it tells us that the same influences prevent and
produce change in the condition of the Animal Kingdom. Facts are all
against it; there is not a fact known to science by which any single
being, in the natural process of reproduction and multiplication, has
diverged from the course natural to its kind, or in which a single kind
has been transformed into any other. But this once established, and
setting aside the idea that Embryology is to explain to us the origin as
well as the maintenance of life, it yet has most important lessons for
us, and the field it covers is constantly enlarging as the study
is pursued. The first and most important result of the science of
Embryology was one for which the scientific world was wholly unprepared.
Down to our own century, nothing could have been farther from the
conception of anatomists and physiologists than the fact now generally
admitted, that all animals, without exception, arise from eggs. Though
Linnaeus had already expressed this great truth in the sentence so often
quoted,--"