Origin of Species Variorum

→ groups 1859 1860 1861

or more groups 1866 1869 1872

→ if 1859 1860 1861 1866 1869

in their adult condition, if 1872

→ the same or 1859 1860 1861

closely 1866 1869 1872

→ the same or nearly similar parents, 1859 1860 1861

the same parent-form, 1866

one parent-form, 1869 1872

→ in that degree 1859 1860 1861

OMIT 1866 1869 1872

→ descent. 1859 1860 1861

descent; but dissimilarity in embryonic development does not prove discommunity of descent, for in one of two groups all the developmental stages may have been suppressed, or may have been so greatly modified as no longer to be recognised, through adaptations, during the earlier periods of growth, to new habits of life. 1866

descent; but dissimilarity in embryonic development does not prove discommunity of descent, for in one of two groups the developmental stages may have been suppressed, or may have been so greatly modified through adaptation to new habits of life, as to be no longer recognisable. 1869 1872

↑ 1 blocks not present in 1859 1860 1861 1866 1869; present in 1872

Even in groups, in which the adults have been modified to an extreme degree, community of origin is often revealed by the structure of the larvæ; we have seen, for instance, that cirripedes, though externally so like shell-fish, are at once known by their larvæ to belong to the great class of crustaceans.

→ It will reveal this community of descent, however much the structure of 1859 1860 1861

Community of descent will, however, often be revealed, although the structure of 1866

Even in groups, in which 1869

→ modified and obscured; 1859 1860 1861

greatly modified and thus obscured; 1866

modified to an extreme degree, community of origin is often revealed by the structure of the larvæ; 1869

→ can 1859 1860 1861

though externally so like shellfish, can 1866

though externally so like shell-fish, are 1869

→ embryonic state of each species and group of species partially 1859 1860 1861

embryonic state of each species and group of species 1866

structure of the embryo generally 1869

embryo often 1872

→ the 1859 1860 1861

more or less completely the 1866

more or less plainly the 1869 1872

→ ancient progenitors, 1859 1860 1861 1866

and ancient progenitor, 1869

and ancient progenitor of the group, 1872

→ of life should resemble 1859 1860 1861 1866

so often resemble 1869

so often resemble in their adult state 1872

→ their descendants,— our 1859 1860 1861

our 1866

OMIT 1869 1872

→ species. 1859 1860 1861

species, their descendants. 1866

species in the same class. 1869

species of the same class. 1872

→ but I am bound to confess that I only hope 1859 1860 1861 1866

and I hope 1869

and we may hope hereafter 1872

→ the law hereafter proved 1859 1860 1861 1866

it hereafter shown in most cases 1869

the law proved 1872

→ now supposed to be represented in existing embryos, 1860 1861 1866

now supposed to be represented in many embryos, 1859

of the progenitor of the group 1872

OMIT 1869

→ in a long course of modification 1859 1860 1861

OMIT 1866 1869 1872

→ age, or 1859 1860

period of growth, or 1861 1869 1872

period of growth, nor 1866

→ of resemblance of ancient forms of life 1859 1860 1861 1866

may be true, but yet, owing 1869 1872

→ embryonic stages of recent forms, may be true, but yet, owing to the 1859 1860 1861 1866

OMIT 1869 1872

→ slight modifi- cations not appearing, 1860

slight modifications not appearing, 1859 1861

slight modifications not having appeared, 1866

modifications 1869

variations 1872

and in so far it reveals the structure of its progenitor. In two →groups of

animal,

animals,

however much they may

~~at present~~

at present

differ from each other in structure and

habits

habits,

→if they pass through →the same or similar embryonic stages, we may feel

almost assured

assured

that they

have

all are

have both

descended from →the same or nearly similar parents, and are therefore →in that degree closely related. Thus, community in embryonic structure reveals community of →descent. ↑ →It will reveal this community of descent, however much the structure of the

adults

adult

~~may~~

may

have been →modified and obscured; we have seen, for instance, that

cirripedes,

cirripedes

→can at once

known

be recognised

by their larvæ

to belong

as belonging

to the great class of crustaceans. As the →embryonic state of each species and group of species partially shows us →the structure of

its

the

their

less modified →ancient progenitors, we can

~~clearly~~

clearly

see why ancient and extinct forms →of life should resemble the embryos of →their descendants,— our existing →species. Agassiz believes this to be a

universal law

law

of nature; →but I am bound to confess that I only hope to see →the law hereafter proved true. It

can,

can

however, be

proved true

only in

those cases

~~alone~~

alone

in which the ancient

state

state,

→now supposed to be represented in existing embryos, has

~~not~~

not

been

obliterated

wholly obliterated

wholly obliterated,

obliterated,

neither

either

~~the~~

the

successive variations →in a long course of modification having

super- vened

supervened

at a very early →age, or by

such

the

variations having been inherited at an earlier

age

period

than that at which they first appeared. It should also be borne in mind, that the

~~supposed~~

supposed

law →of resemblance of ancient forms of life to the →embryonic stages of recent forms, may be true, but yet, owing to the geological record not extending far enough back in time, may remain for a long period, or for ever,

in- capable

incapable

of demonstration.

Thus, as it seems to me, the leading facts in embryology, which are second

~~in importance~~

in importance

to none in

importance,

natural history,

are explained on the principle of →slight modifi- cations not appearing,