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Ap 18th 1856

Mr. Wollaston

Helix Wollastoni, f. on s. slope of certain mountains in P. Santo, alive by hundred & no where else living on island. But abundant in terrestrial Pliocene formation at base of mountain in 2 spots & no where else. There are some other analogous facts. It is like Benthams Pyrenes plants excessively local & yet most abundant.─ & most ancient Mr W. thinks that most of the endemic forms do not no tendency to spread, (but he had never thought of checks). But I think these checks must hold good; anyhow at base of mountains they mingle with lowland forms. (& the rapid increase of intermediate forms.)

In our country the varying number of slugs & snails & their occasional extraordinary increase shows that they are at least capable of increase. But these facts are most wonderful to the wondrous balance [nicely] of balance of powers, & this is so wonderful that it is opposed

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the Balance of powers struggle for increase ─ During time elapsed there must have been (& indeed Lyell asserts changes of condition since fossil beds deposited) & this shows, on the view of this species spread being checked by other organisms, that the struggle must be with other organise beings.

There are so many that it is the rule that species & varieties are al fixed case to its own mountain.─

Wollaston says there are most striking instances of species formerly most abundant, now become most rare & confined in state & gone to die, as he puts it, on certain mountain ─ summit. ─ ie rarity precedes extinction.─

Wollaston asserts most positively that if hundreds of forms of same species were thrown

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together, he could pick at variation from different mountains & islets: that this is the rule: that he could distinguish the same insect from P. Santo & Madeira.

Here these all have tendency to form differences in each spot, whatever the cause may be.─ We shd remember that these islds have long been stocked with mollusca; & with I think. This number of species (in this land of pulmoniferous mollusca) & confined range shows very close adaptation & long occupation, & is analogous to Erica at C. of Good Hope.─

But W. says that Helix polymorpha (or bisana) has varieties from several mountains, (as H. attrita of Lowe) which are absolutely constant

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I understand, very few European forms which have not been introduced. Hence we may suppose species most rarely introduced.

The extraordinary isolation & adaptation of forms harmonises splendidly with view matured when with Lyell, that P. Santo forms do not spread in Madeira, because no great advantage.─

Can the spreading of British Sanchus in N Zealand be owing to advantage of change of seed.─

Can the mollusca & insects fight: can their numbers & Elaterida & Thterophages Thalerophagous mollusca here are relation. I think then in larva condition feed on roots?

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on certain mountains, has intermedial forms at base, when it blends into the lowland wide spread forms.─ now destroy their forms & you have 2 species.─ But then comes in question of antiquity. Even If most of their varying forms ie not parent were not fossil it wd be splendid.─ When I reflect on Birds of Madeira (& marine shells in opposition to land / & both opposed to Galapagos, I am deeply impressed with crossing bearing a most important part (& vigour given by a cross) & I can understand it by no other agency. No doubt isld of great Britain infinitely modern owing to glacial epoch, & proximity for greater forming crosses eve of man, if not by other means.

W. was strong that all the Madeira forms have one type, so the even Lowe

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as a joke once asked "whether all were not one species?" Yet I cannot make out whether more than one type ─ did not seem to have thought whether P. Santo & Madeira type different. But really the shells are so isolated in P. Santo, that the sea seem to make no great difference; & perhaps this explains the wonderfully dissimilarity of conchology of Madeira & P. Santo.

The wonderful spreading of Linnæus within Lowes life-time are the tops of mountains; so that not floods ─ it must be with larvæ after breaking out of eggs ─ the horses or man legs?

There seem to be very few Mollusca common to Europe & Madeira, which have not been introduced by man.

Bulinus lubricus, seem to have varied very slightly since introduced by man.

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Some of the few land-shells on insects?? Fd on summit common with Europe are f. only on summit, these must have immigrated during glacial epoch.

One Madeira Land-shell show an American affinity.─

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With respect to migration from S. to north (cannot run fr n. to s) W. seems to have no good evidence in mollusca. He relies on endemic forms, as Tarphius with 1 species in Sicily & Hegetes many in Canaries & 1 in P. Santo: he looks at where most species in present spot; I doubt how far this can be trusted especially when a peculiar isolated spot not well stocked. Many species show that form in question long resident there.─ Anyhow the migration may have been long ago. can Of the few insects common to Europe not endemic; they are European.─

Heer has written paper on Land-shells of Madeira. ─ Lyell has it─

Wollaston says Pupa & many other land shells present abrupt difference in size, & Cla [illeg] lia; over which range some big, & some small.─

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April. 28/56/ Wollaston Entomology.

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I cannot make out any Tropical species in Madeira.─

Range seems not to throw any light in absence in absence of Thalerophagous lamellicorn & Elateridæ (ie those of very general distribution) then by 1 species of each, certainly rather strongly make me think that condition not favouring favouring development must be cause.─

The number of insects large for so small an isld.─

As A. Decandolle & Wollaston both give up many species & yet stop at next stage: this must be argued.─