Origin of Species Variorum

→ OMIT 1872

no less than 1861

→ besides 1872

of structure; he makes 1861

→ of aggregated simple eyes. 1872

namely, "aggregates" of stemmata, and he adds that "this is the transition-form between the mosaic-like compound eyes unprovided with a concentrating apparatus, and organs of vision with such an apparatus." 1861

↑ 2 blocks not present in 1861 1866 1869 1872; present in 1859 1860

In certain crustaceans, for instance, there is a double cornea, the inner one divided into facets, within each of which there is a lens-shaped swelling. In other crustaceans the transparent cones which are coated by pigment, and which properly act only by excluding lateral pencils of light, are convex at their upper ends and must act by convergence; and at their lower ends there seems to be an imperfect vitreous substance.

→ When we reflect on 1866 1869 1872

With 1859 1860 1861

→ with respect to the wide, diversified, and graduated range of structure 1869 1872

and imperfectly given, which show that there is much graduated diversity 1859 1860

and imperfectly given, which show how much graduated diversity 1861

and imperfectly, with respect to the wide, diversified, and graduated range of structure 1866

→ in 1859 1860 1866 1869 1872

there is in 1861

→ the lower animals; and when we bear 1869 1872

living crustaceans, and bearing 1859 1860

our existing crustaceans, and bearing 1861

the existing Articulata; and when we bear 1866

→ all living forms must be in comparison with 1866 1872

living animals is in proportion to 1859 1860 1861

all the forms now living must be in comparison with 1869

→ the difficulty ceases to be 1866 1869 1872

I can see no 1859 1860 1861

→ OMIT 1869 1872

difficulty (not more than in the case of many other structures) 1859 1860 1861

(not more so than in the case of many other structures) 1866

→ ought not to hesitate to go one step further, if 1869 1872

if 1859 1860 1861 1866

→ modification through natural selection; he ought 1872

descent, ought not to hesitate to go further, and 1859 1860 1861

descent with modification, ought not to hesitate to go further, and 1866

descent with modification; he ought 1869

→ OMIT 1869 1872

the eye of 1859 1860 1861 1866

→ eye might thus 1872

might 1859 1860 1861 1866

eye might 1869

→ OMIT 1872

by natural selection, 1859 1860 1861 1866 1869

→ the modifications were all 1872

all the modifications were 1869

that

Müller

makes

formerly made

three main

classes,

classes

with →OMIT seven

sub-divisions

subdivisions,

→besides a fourth main

class,

class

→ of aggregated simple eyes. ↑ →When we reflect on these facts, here

far

given

~~given much~~

given much

too

briefly

briefly,

→with respect to the wide, diversified, and graduated range of structure →in the eyes of →the lower animals; and when we bear in mind how small the number of →all living forms must be in comparison with those which have become extinct, →the difficulty ceases to be very great →OMIT in believing that natural selection

has

may have

converted the simple apparatus of an optic

nerve

nerve,

merely

....

coated with pigment and invested by transparent membrane, into an optical instrument as perfect as is possessed by any member of the

great

....

Articulate

class.

Class.

He who will go thus far, →ought not to hesitate to go one step further, if he

find

should find

finds

on finishing this

treatise

volume

that large bodies of facts, otherwise inexplicable, can be explained by the theory of →modification through natural selection; he ought to admit that a structure even as perfect as →OMIT an

eagle

eagles

eagle's

→eye might thus

have been

formed

formed,

→OMIT although in this case he does not know

any of

....

the transitional

grades.

steps.

states.

It has been objected that in order to modify the eye and still preserve it as a perfect instrument, many changes would have to be effected simultaneously, which, it is assumed, could not be done through natural selection; but as I have attempted to show in my work on the variation of domestic animals, it is not necessary to suppose that →the modifications were all simultaneous, if they were extremely slight and gradual. Different kinds of modification would, also, serve for the same general purpose: as Mr. Wallace has remarked, "if a lens has too short or too long a focus, it may be amended either by an alteration of curvature, or an alteration of density; if the curvature be irregular, and the rays do not converge to a point, then any increased regularity of curvature will be an improvement. So the contraction of the iris and the muscular movements of the eye are neither of them essential to vision, but only improvements which might have been added and perfected at any stage of the construction of the instrument." Within the highest division of the animal kingdom, namely, the Vertebrata, we can start from an eye so simple, that it consists, as in the lancelet, of a little sack of transparent skin, furnished with a nerve and lined with pigment, but destitute of any other apparatus. In fishes and reptiles, as Owen has remarked, "the range of gradations of dioptric structures is very great." It is a significant fact that even in man, according to the high authority of Virchow, the beautiful crystalline lens is formed in the embryo by an accumulation of epidermic cells, lying in a sack-like fold of the skin; and the vitreous body is formed