My dear Henslow

We are now beating up the Rio Plata, & I take the opportunity of beginning a letter to you.— I did not send off the specimens from R Janeiro; as I grudged the time it would take to pack them up.— They are now ready to be sent off, & most probably by the Packet.—² If so they go to Falmouth (where C. FitzRoy has made arrangements) & so will not trouble your Brothers agent in London.—

When I left England.—I was not fully aware how essential a kindness you offered me, when you undertook to receive my boxes.— I do not know what I should do without such head-quarters.— And now for an apologetical prose about my collection.— I am afraid you will say it is very small.—but I have not been idle & you must recollect that in lower tribes, what a very small show hundreds of species make.— The box contains a good many geological specimens.— I am well aware that the greater number are too small.— But I maintain that no person has a right to accuse me, till he has tried carrying rocks under a Tropical sun.— I have endeavoured to get specimens of every variety of rock, & have written notes upon all.— If you think it worth your while to examine any of them, I shall be very glad of some mineralogical information, especially in any numbers between 1 & 254, which include St Jago rocks.— By my Catalogue, I shall know which you may refer to.—³ As for my Plants, “pudet pigetque mihi”.⁴ All I can say is that when objects are present which I can observe & particularize about, I cannot summon resolution to collect where I know nothing.—

It is positively distressing, to walk in the glorious forest, amidst such treasures, & feel they are all thrown away upon one.— My collection from the Abrolhos is interesting as I suspect it nearly contains the whole flowering Vegetation, & indeed from extreme sterility the same may almost be said of St Jago.— I have sent home 4 bottles with animals in spirits I have three more, but would not send them till I had a fourth.— I shall be anxious to know how they fare.— I made an enormous collection of Arachnidæ at Rio.— Also a good many small beetles in pill-boxes; but it is not the best time of year for the latter.— As I have only $\frac{3}{4}$ of a case of Diptera &c I have not sent them.— Amongst the lower animals, nothing has so much interested me as finding 2 species of elegantly coloured true Planariæ,⁵ inhabiting the dry forest! The false relation they bear to Snails is the most extraordinary thing of the kind I have ever seen.— In the same genus (or more truly family) some of the marine species possess an organization so marvellous.—that I can scarcely credit my eyesight.— Every one has heard of the discoloured streaks of water in the Equatorial regions.— One I examined was owing to the presence of such minute Oscillaria that in each square inch of surface there must have been at least one hundred thousand present.— After this I had better be silent.— for you will think me a Baron Munchausen⁶ amongst Naturalists.— Most assuredly I might collect a far greater number of specimens of Invertebrate animals if I took less time over each: But I have come to the conclusion, that 2 animals with their original colour & shape noted down, will be more valuable to Naturalists than 6 with only dates & place.— I hope you will send me your criticisms about my collection; & it will be my endeavour that nothing you say shall be lost on me.—

I would send home my writing with my specimens, only I find I have so repeatedly occasion to refer back, that it would be a serious loss to me.— I cannot conclude about my collections, without adding that I implicitly trust in you keeping an exact account against all the expense of boxes &c &c.— At this present minute we are at anchor in the mouth of the river: & such a strange scene as it is.— Every thing is in flames,—the sky with lightning,—the water with luminous particles, & even the very masts are pointed with a blue flame.— I expect great interest in scouring over the plains of M Video, yet I look back with regret to the Tropics, that magic line to all Naturalists.— The delight of sitting on a decaying trunk amidst the quiet gloom of the forest is unspeakable & never to be forgotten.— How often have I then wished for you.—when I see a Banana, I well recollect admiring them with you in Cambridge.—little did I then think how soon I should eat their fruit.—

August 15^th. In a few days the Box will go by the Emulous Packet (Captⁿ. Cooke) to Falmouth & will be forwarded to you.— This letter goes the same way so that if in course of due time you do not receive the box, will you be kind enough to write to Falmouth.— We have been here (Monte Video) for some time; but owing to bad weather & continual fighting on shore have scarcely ever been able to walk in the country.— I have collected during the last month nothing.— But to day I have been out & returned like Noahs ark.—with animals of all sorts.— I have to day to my astonishment found 2 Planariæ living under dry stones. Ask L Jenyns if he has ever heard of this fact. I also found a most curious snail & Spiders, beetles, snakes, scorpions ad libitum And to conclude shot a Cavia weighing a cwt:— On Friday we sail for the Rio Negro, & then will commence our real wild work.— I look forward with dread to the wet stormy regions of the South.— But after so much pleasure I must put up with some sea-sickness & misery.—

Remember me most kindly to every body & believe me, my dear Henslow, Yours affectionately | Chas. Darwin *S 2

Monte Video. August 15^th.—