Origin of Species Variorum

→ but some few 1869 1872

some strictly 1859 1860 1861 1866

→ in regard to 1869 1872

on the distribution of 1859 1860 1861 1866

↑ 3 blocks not present in 1869 1872; present in 1859 1860 1861 1866

It should be observed that the northern species and forms found in the southern parts of the southern hemisphere, and on the mountain-ranges of the intertropical regions, are not arctic, but belong to the northern temperate zones. As Mr. H. C. Watson has recently remarked, "In receding from polar towards equatorial latitudes, the Alpine or mountain floras really become less and less arctic." Many of the forms living on the mountains of the warmer regions of the earth and in the southern hemisphere are of doubtful value, being ranked by some naturalists as specifically distinct, by others as varieties; but some are certainly identical, and many, though closely related to northern forms, must be ranked as distinct species.

→ whether Mr. Croll's conclusion that when the northern hemisphere suffered from the extreme cold of the great Glacial period, the southern hemisphere was actually warmer, throws any clear light 1872

what light can be thrown 1859 1860 1861 1866

whether Mr. Crolls conclusion that when the northern hemisphere suffered from the extreme cold of the great Glacial period, the southern hemisphere was actually warmer, throws any clear light 1869

→ present apparently inexplicable distribution of various organisms in the temperate parts of both hemispheres, and on the mountains of the tropics. 1872

foregoing facts, on the belief, supported as it is by a large body of geological evidence, that the whole world, or a large part of it, was during the Glacial period simulta- neously much colder than at present. 1859

foregoing facts, on the belief, supported as it is by a large body of geological evidence, that the whole world, or a large part of it, was during the Glacial period simultaneously much colder than at present. 1860 1861

foregoing facts, on the belief, supported as it is by a large body of geological evidence, that the whole world, or a large part of it, was simultaneously colder during the Glacial period than at present. 1866

present apparently inexplicable distribution of various organisms in the temperate parts of both hemispheres, and on mountains of the tropics. 1869

that these plants are not strictly

Arctic

arctic

forms; for, as Mr. H. C. Watson has remarked, "in receding from polar towards equatorial latitudes, the Alpine or mountain floras really become less and less Arctic." Besides these identical and closely allied forms, many species inhabiting the same widely sundered areas, belong to genera not now found in the intermediate tropical lowlands.

This

These

brief

abstract applies

remarks apply

to plants

alone:

alone;

→but some few analogous facts could be given →in regard to terrestrial animals. In marine productions, similar cases

occur;

likewise occur;

as an example, I may quote a

remark

statement

by the highest authority, Prof. Dana, that

"it

is certainly a wonderful fact that New Zealand should have a closer resemblance in its crustacea to Great Britain, its antipode, than to any other part of the

world."

Sir J. Richardson, also, speaks of the reappearance on the shores of New Zealand, Tasmania,

&c,

&c.,

of northern forms of fish. Dr. Hooker informs me that twenty-five species of Algæ are common to New Zealand and to Europe, but have not been found in the intermediate tropical seas.

From the foregoing facts,

namely

namely,

the presence of temperate forms on the highlands across the whole of equatorial Africa, and along the Peninsula of

India

India,

to Ceylon and the Malay

archipelago,

Archipelago,

and in a less well-marked manner across the wide expanse of tropical South America, it appears almost certain that at some former period, no doubt during the most severe part of

the

Glacial period, the lowlands of these great continents were everywhere tenanted under the equator by a considerable number of temperate forms. At this period the equatorial climate at the level of the sea was probably about the same with that now experienced at the height of from five to six thousand feet under the same

latitudes,

latitude,

or perhaps even rather cooler. During this, the coldest period, the lowlands under the equator must have been clothed with a mingled tropical and temperate vegetation, like that described by Hooker as growing luxuriantly at the height of from four to five thousand feet on the lower slopes of the Himalaya, but with perhaps a still greater preponderance of temperate forms. So

again,

again

the mountainous island of Fernando Po, in the Gulf of Guinea, Mr. Mann found temperate European forms beginning to appear at the height of about five thousand feet. On the mountains of Panama, at the height of only two thousand feet, Dr. Seemann found the vegetation like that of Mexico, "with forms of the torrid zone harmoniously blended with those of the temperate." ↑

Now let us see →whether Mr. Croll's conclusion that when the northern hemisphere suffered from the extreme cold of the great Glacial period, the southern hemisphere was actually warmer, throws any clear light on the →present apparently inexplicable distribution of various organisms in the temperate parts of both hemispheres, and on the mountains of the tropics.