Dear Darwin

I have finished the reading of your mss. & have been very much delighted & instructed.¹ Your case is a most strong one & gives me a much higher idea of change than I had previously entertained; &, though, as you know, never very stubborn about unalterability of specific type, I never felt so shaky about species before. The first half you will be able to put more clearly when you polish up, I have in several cases made pencil alterations in details as to words &c, to enable myself to follow better—some of it is rather stiff reading. ² I have a page or two of notes for discussion, many of which were answered as I got further on with the mss., more or less fully.³

Your doctrine of the cooling of the tropics is a startling one, when carried to the length of supporting plants of cold-temperate regions, & I must confess that, much as I should like it, I can hardly stomach keeping the Tropical genera alive in so very cool a greenhouse. Still I must confess that all your arguments pro may be much stronger put than you have

I am more reconciled to Iceberg transport than I was also, the more especially as I will give you any length of time to keep vitality in ice, & more than that will let you transport roots that way also— Many of these subjects which I never myself studied for myself, I wanted put in the systematic form you have put them, for proper appreciation—

I think that you might support your cause by making more use of gulf streams & oblique lines of transport—you appear to dwell too much upon meridional lines of migration This mode of handling at once suggested the Query are the Arctic & Antarctic American genera more allied than the Tasmanian & Siberian—the former offering every possible facility in continuous land,—the latter none.— It also makes you appear to shirk the question of transport from E to W. or vice versa.— you offer no explanation of the vegetation (not littoral) of Abyssinia & Indian Penins. being so similar; of the Carnatic, Ava, & N.W. Australia being in so many points alike—of the curious parallels or representatives between Madagasca, Ceylon & the Sunda Islands. In short Meridional migration alone occupies you. Nor do I like putting Iceland, Ferroe, & Spitzbergen out of the Category of the glacially peopled countries, & leaving Shetlands Orkneys Scotland in it. This is however a trifle.

Ch. Martins arguments seem to apply no more to these islands than to any other area Continental or insular—⁴ If they presented any anomalies as the presence of Lapland plants or Greenland ones I might then believe them to be peopled by accidental migration, but if Icebergs are to be so powerful why did they bring no Greenland, American or other plants to these Islands, which are so well situated for the purpose.

Thanks for your note received this morning— We shall hope (if not look) for you on Wednesday to meet Lindley & Henslow.—or on Friday to meet Tyndall & Henslow.⁵

Owen I hear committed a cutting telling & flaying alive assault on Huxleys adaptation views at the Geolog. Soc. & read it with the cool deliberation & emphasis & pointed tone & look of an implacable foe.—& H. I fear did not defend himself well (though with temper) & perhaps had not a popular champion in Carpenter who barbed him— These embroglios are very bad indeed & must insensibly have a bad effect upon Huxley—the best natures insensibly deteriorate under such trials.⁶

I shall bring your mss to the Club in the Club box so you need not come on purpose.—⁷ I shall be really glad of more.

Ever most sincerely yrs | Jos D Hooker

P.S. Was it not with you? that I argued that Lyell had assumed as demonstrable a change in the temp of the whole globe to be producable by altered condition of surface see Principles 9^th Ed. 103, 104⁸

[Memorandum]⁹

Note I.¹⁰ Would Forbes suppose that the presence of the South Shetland Aira Antarctica on the Falklands was due to Iceberg transportation North?¹¹ Is it not more natural to suppose that A. Ant. was produced by creation or variation on the American continent & thence either transported South to S. Shetland or that it inhabited an intermediate sunk area. I am against making arctic regions centres of creation either by variation or by specific creation.

I think it would facilitate our researches much not to look beyond the epoch of the existence of those continents having the required climate for the existence of the scattered productions whose migrations we seek to account for. It is enough to admit a glacial land & sea over central Europe & do not let us speculate on the origin of its species. Never wander further back into Geological time than is necessary—it bewilders.

On the whole then I would perhaps confine this part of the discussion to the migration North & vertical ascent of species inhabiting a cold country.

Note B.¹² Might not much of this difficulty be got over by supposing the E & W. parts of the glacial continent differently heated, & that currents flowed East & West or NE & NW.

Thus the connecting land of Europe & America might be much warmer than those parts of either continent in the same latitude where the mountains were

Note C.¹³ I cannot see why the colonization of Iceland Ferroe & Spitzbergen should come under a different category from other lands—this is most unphilosophical Surely a theoretical inflexion of the isothermals should not be wholly lost sight of, during the glacial epoch, as it manifestly is after it. The gradual accession of the Gulf Stream influence would warm all that part of the glacial sea coast or chain of Islands that included Iceland Ferroe &c before any other part of the glacial region & induce migration along that line, however cold the preexisting arctic desert in which they were situated may be assumed to be

Note D.¹⁴ I cannot understand this. Why do the Gentians not go North? these not being more Alpine than the Arctic species— Why should they have spread over the intervening country?

Note E.¹⁵ Then why no peculiar species or varieties in Iceland, Spitzbergen &c.

Note F¹⁶ The same argument must hold for the Arctic & Antarctic representative Crustacea—on which Ross was always insisting & swearing that some were identical with what he had described in Capt. Parry Voy &c¹⁷

Note G¹⁸ In fact the Flora of analogous elevations of Ceylon, Nilghiri, Khasia & Himal is to great extent specifically the same

Note H.¹⁹ After which why did not any ascend the Himalaya?

An argument in favor of alteration induced by isolation afforded by fact that so many well known species when found isolated have as much differences as to deceive botanists & then when dried lose all distinguishing characters

Change of Tropical Climate demanded is far too great Where were many tropical genera & orders— Also migration not always N. & S. but across continents obliquely— Also all this leaves longitudinal distribution unaccounted for as Abyssinia & India—W. Austral & Carnatic.

Ordinary laws of reproduction includes modif. of specific forms.

But it is improbable that similar forms be generated from specifically different parents in different places

Hence will propagation account for presence of identical forms in all parts of globe

Plants, insects—common to Alps & Scandinavia Steinbock, variable Hare, Chamois.

Forbes glacial epoch accounts for this

Help may be got by introducing humidity as an element—quote very different levels on Himal. Khasia & Ceylon for same species.²⁰