National opinion. [volume] (Bradford, Vt.) 1865-1874, 1873-04-11
All Life ORIGINATING In Eggs.

sss ssss' W. 'S'''"''''o
In the first place, at the very outset
says Prof. Agassiz in late lecture, W,
find one singular, universal fact. Al
animals, without exception, high or low,
of whatever ultimate compexity Oh
simplicity of structure, originate from
eggs, and from eggs OF the same char
acter. | do not mean TO be understood
that there is no other mode OF multi
plying. Some animals, rs corals, foi
instance, many hydroids, and other low
organisms, reproduce themselves by
budding or by division of the parent
stock. But they also, at some time or
other, produce eggs, and thus bear their
testimony to the general law OF nature
which applies to the whole animal king
dom without exception. Indeed, the
seed in plants has the same structure as
the so-called ovarian egg in animals,
and thus we may speak of all organized
beings, vegetable or animal, rs multi
plying by eggs. The discovery that
this great law applies to the higher ami
mails also, is comparatively recent. 1t
is only 80 years since Carl Ernst Won
Baer made his wonderful researches on
the egg of the dog and rabbit, and an
nounced that the mammal has an ovarian
egg identical with that of all other yer,
tebrates and with that Of articulates,
mollusks and radiates. The discovery
OF this universal law that all organized
beings multiply by the same means, is
certainly one of the greatest and most
startling congratulations of modern
times. 1t gives lis the broadcast ground
for our inquiry into their ultimate rela-
tions since they have all one starting
point. At first it may seem to simplify
the inquiry: But the moment We leave
tho point at which all animals seem
alike, and enter upon the various phases
and transformations to be gone through
before they reach the adult condition,
field of study opens before us sufli-
cent to fill many lifetimes. We come
upon series of phenomena OF the
deepest interest, but often in their first
aspect very perplexing. There are
transient PLACES in the growth of the
higher animals during which they re-
semble the permanent final conditions
Of adult animals lower down in the
same type, having, that is, like struc-
ture, but OF inferior development.
These comparisons cannot, however, be
carried on outside the limits of one and
the same type. To this circumscription
OF the law allnded when, in the earlier
part Of my lecture, spoke Of limita-
ions in the natural fundamental rela-
tons OF animals You may compare a
quadruped in certain phases OF its
growth with the adult condition OF some
lower kinds of vertebrates and be
amazed at the resemblance, but you can
not carry the comparison over into the
type OF artculates or into any other
type OF the animal kingdom based upon
a different plan. Within each type the
has character as distinct
as the plan on which the type is built
An insect, for instance, can never at any
time OF its development, after it has
passed out Of that universal condition
Of the ovarian egg to which alluded,
be compared to an oyster or fish, but
it passes through phases where it can
hardly be distinguished from a worm
that is, in the course Of its development
it bears transient likeness to the adult
OF being standing lower in
the type of articulates to which they
both belong In short, every animal
belonging to any one of the higher
groups, during the transformations by
which he reaches the adult state may
pass through modified conditions, in
each of which he resembles some being
of his own type of the animal kingdom
for whom that condition is final Enough
is known of the transformations of ami
mails now to make this generalization
perfectly trustworthy one, although the
number Of illustrations is small. The
study of embryology is exceedingly
difficult, and the sacrifice of specimens
is very great in order to obtain the COM
plete history of the growth of any one
animal. The progress of these investi-
cations must necessarily be slow, be-
cause theyar solaborious and so costly,
but they have already assumed sequence
and conference enough to afford sound
basis for the result l have just given.
While the phases of growth and resem-
blance have been followed, the limita-
tons keeping each primary type within
its own boundaries have not been sutfi-
GENTLY considered, and are, indeed,
generally wholly lost sight Of This
carelessness of investigation or of state
ment gives currency to broad generali-
cations, partially tr le indeed, but false
when they are made to cover too wide
ground.