Origin of Species Variorum

→ projecting 1869 1872

and this projects outwardly 1866

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

In the Articulata we can commence a series with an optic nerve merely coated with pigment, and without any other mechanism; and from this low stage, numerous gradations of structure, branching off in two fundamentally different lines, can be shown to exist, until we reach a moderately high stage of perfection.

→ OMIT 1869 1872

look for gradations, we 1866

→ the latter sometimes forming 1869 1872

which sometimes forms 1866

→ facets on the cornea of the 1869

cones surrounded by pigment, which form the 1866

facets on the cornea of their 1872

→ form true lenses, and that the cones include curiously modified nervous filaments. 1869 1872

are filled with transparent refractive matter, and these cones produce images; but in addition, in certain beetles the facets of the cornea are slightly convex both externally and internally,—that is, are lens-shaped. 1866

→ But these organs 1869

Altogether so diversified is the structure of the eye 1866

→ are so much diversified that Müller formerly made 1869

that Müller makes 1866

→ OMIT 1869

with seven subdivisions, 1866

→ with seven subdivisions, besides 1869

and he adds 1866

→ 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 the forms now living must be in comparison with 1869

living animals is in proportion to 1859 1860 1861

all living forms must be in comparison with 1866 1872

→ 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

the nerve are filled, as described by the author just quoted, with transparent gelatinous matter, →projecting with a convex surface, like the cornea in the higher animals. He suggests that this

structure

....

serves not to form an image, but only to concentrate the luminous rays and render their perception more

perfect.

easy.

In this concentration of the rays we gain the first and by far the most important step towards the formation of a

true

true,

....

picture-forming eye; for we have only to place the naked extremity of the optic nerve, which in some of the lower animals lies deeply buried in the

body

body,

and in some near the surface, at the right distance from the concentrating apparatus, and an image

must

will

be formed on it. ↑

In the great class of the Articulata,

....

we →OMIT may start from an optic nerve simply coated with pigment, →the latter sometimes forming a sort of pupil, but

....

destitute of a lens or other optical contrivance. With insects it is now known that the numerous →facets on the cornea of the great compound

eyes,

eyes

→form true lenses, and that the cones include curiously modified nervous filaments. →But these organs in the Articulata →are so much diversified that Müller formerly made three main

classes,

classes

→OMIT of compound

eyes,

eyes

→with seven subdivisions, besides a fourth main class of aggregated

simple-eyes.

simple eyes.

→When we reflect on these facts, here

far

given much

~~given~~

given

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 the forms now living 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~~

great

Articulate

class.

Class.