Origin of Species Variorum

→ different 1869 1872

great existing differences in the 1861 1866

→ within each 1869

which occur within almost every 1861 1866

within the same 1872

→ vertebrata, to the co-existence 1869 1872

co-existence 1861 1866

→ fish— amongst mammalia, 1869 1872

fish in the vertebrata,— 1861 1866

→ fishes, to the co-existence 1869 1872

mammalia— or 1861 1866

→ lancelet (Branchiostoma), 1866 1869

amphioxus, 1861

the lancelet (Amphioxus), 1872

→ the whole class of mammals, or of certain members in this class, 1869 1872

certain mammals or of the whole class 1861 1866

→ of, and thus exterminating, 1861 1866 1869

of 1872

→ in comparison with fishes. 1869

compared with fishes. 1861 1866

in having to come continually to the surface to breathe. 1872

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

In this latter class, members of the shark family would not, it is probable, tend to supplant the amphioxus; the struggle for existence in the case of the amphioxus apparently will lie with members of the invertebrate classes.

→ In this latter class, 1869

With fishes, 1872

Nearly the same remarks are applicable if we look to the →different grades of organisation →within each great group; for instance,

the →vertebrata, to the co-existence of mammals and →fish— amongst mammalia, to the co-existence of man and the

ornithorhynchus

ornithorhynchus—

amongst →fishes, to the co-existence of the shark and →lancelet (Branchiostoma), which latter fish in the extreme simplicity of its structure

closely

....

approaches the invertebrate classes. But mammals and fish hardly come into competition with each other; the advancement of →the whole class of mammals, or of certain members in this class, to the highest grade

of organisation

....

would not lead to their taking the place →of, and thus exterminating, fishes. Physiologists believe that the brain must be bathed by warm blood to be highly active, and this requires

aërial

respiration; so that warm-blooded mammals when inhabiting the water

lie

live

under

some

disadvantage

disadvantages

→in comparison with fishes. ↑ →In this latter class, members of the shark family would not tend to supplant the lancelet; for the lancelet, as I hear from Fritz

Müller,

has as sole companion and competitor on the barren sandy shore of South Brazil, an anomalous annelid. The three lowest orders of mammals, namely, marsupials, edentata, and rodents, co-exist in South America in the same region with numerous monkeys, and probably interfere little with each other. Although organisation, on the whole, may have advanced and be

advancing

still advancing

throughout the world, yet the scale will

still

always

present

all

many

degrees of perfection; for the high advancement of certain whole classes, or of certain members of each class, does not at all necessarily lead to the extinction of those groups with which they do not enter into close competition. In some cases, as we shall hereafter see, lowly organised forms

seem

appear

to have been preserved to the present

day,

day

from inhabiting

peculiar

confined