Origin of Species Variorum

→ of embryos of different species within the same class, generally, 1859 1860 1861 1866

the general, 1869

the common, 1872

→ each other;— 1859 1860 1861 1866

between the embryos or larvæ 1869 1872

→ structure of 1859 1860 1861 1866

most distinct species in the same class;— 1869 1872

→ not being closely related to its conditions of existence, except when the embryo becomes at any period of life active and has 1859 1860 1861

not being closely related to its conditions of existence, existence, except when the embryo becomes at any period of life active and has 1866

retaining whilst within the egg or womb, structures which are of no service to it, either at that period or later in life; whilst embryos at a later period, or larvæ, which have 1869

often retaining whilst within the egg or womb, structures which are of no service to it, either at that or at a later period of life; on the other hand larvæ, which have 1872

→ itself;— of the embryo apparently having sometimes a higher 1859 1860 1861 1866

their own wants, are perfectly adapted to the surrounding conditions;— and lastly the fact of certain larvæ standing higher in the scale of 1869

their own wants, being perfectly adapted to the surrounding conditions;— and lastly the fact of certain larvæ standing higher in the scale of 1872

→ necessarily 1859 1860 1861 1866

or individual differences necessarily 1869 1872

→ head— indeed the evidence rather 1859 1860 1861 1866

head, but what we have certainly 1869 1872

→ the animal has been born, what its 1859 1860 1861 1866

birth, what the 1869

birth, what will be the 1872

→ form will ultimately turn out. 1859 1860 1861 1866

form of their young animals will turn out. 1869

demerits of their young animals. 1872

→ it is fully 1859 1860 1861 1866

the effects are 1869 1872

→ even before the embryo is formed; and the variation may be due to the male and female sexual elements having been affected by the conditions to which either parent, or their ancestors, have been exposed. 1859 1860 1861 1866

on one or both parents before reproduction. 1869

on one or both parents before the act of generation. 1872

which ultimately become very unlike and serve for diverse purposes, being at

this

early period of growth alike;— →of embryos of different species within the same class, generally, but not

invariable,

universally,

resemblance

resembling

→each other;— of the →structure of the embryo →not being closely related to its conditions of existence, except when the embryo becomes at any period of life active and has to provide for →itself;— of the embryo apparently having sometimes a higher organisation than the mature

animals

animal

animal,

into which

they are

it is

developed.

developed?

I believe that all these facts can be

ex- plained,

follows.

~~the~~

~~view~~

~~descent~~

~~with~~

~~modification.~~

It is commonly assumed, perhaps from monstrosities

~~often~~

often

affecting the

embryos

embryo

at a very early period, that slight variations →necessarily appear at an equally early period.

But we

have little evidence on this →head— indeed the evidence rather points the other way; for it is notorious that breeders of cattle, horses, and various fancy animals, cannot positively tell, until some time after →the animal has been born, what its merits or →form will ultimately turn out. We see this plainly in our own children; we cannot

~~always~~

always

tell whether

the

child will be tall or short, or what its precise features will be. The question is not, at what period of life

each

any

variation

may have

has

been caused, but at what period →it is fully displayed. The cause may have acted, and I believe

often

generally

has acted, →even before the embryo is formed; and the variation may be due to the male and female sexual elements having been affected by the conditions to which either parent, or their ancestors, have been exposed. Nevertheless an effect thus caused at a very early period, even before the formation of the embryo, may appear late in life; as when an hereditary disease, which appears in old age alone, has been communicated to the offspring from the reproductive element of one parent. Or