Dear Jenyns

I have taken a most ungrateful length of time in thanking you for your very kind present of your Observations.¹ But I happened to have had in hand several other books & have finished yours only a few days ago. I found it very pleasant reading & many of your facts interested me much: I think I was more interested, which is odd, with your notes on some of the lower animals than on the higher ones. The introduction struck me as very good; but this is what I expected, for I well remember being quite delighted with a preliminary essay to the first number of the Annals of N. History.²

I missed one discussion, & think myself illused, for I remember your saying you would make some remarks on the weather & Barometer,³ as a guide for the ignorant in prediction. I had, also, hoped to have perhaps met with some remarks on the amount of variation in our common species: Andrew Smith once declared he would get some hundreds of specimens of larks & sparrows from all parts of Great Britain & see whether with finest measurements he c^d detect any propor-tional variations in beaks or limbs &c. This point interests me from having lately been skimming over the absurdly opposite conclusions of Glöger⁴ & Brehm;⁵ the one making half-a dozen species out of every common bird & the other turning so many reputed species into one. Have you ever done anything of this kind; or have you ever studied Gloger’s or Brehm’s works?⁶

I was interested by your account of the Martins, for I had just before been utterly perplexed by noticing just such a proceeding as you describe; I counted seven one day lately visiting a single nest & sticking dirt on the adjoining wall.⁷ I may mention that I once saw some squirrels eagerly splitting those little semi-transparent spherical galls on the back of oak-leaves, for the maggot within; so that they are insectivorous.— A Cychrus rostratus once squirted into my eye & gave me extreme pain; & I must tell you what happened to me on the banks of the Cam in my early entomological days; under a piece of bark I found two carabi (I forget which) & caught one in each hand, when lo & behold I saw a sacred Panagæus crux major; I could not bear to give up either of my Carabi, & to lose Panagæus was out of the question, so that in despair I gently seized one of the carabi between my teeth, when to my unspeakable disgust & pain the little inconsiderate beast squirted his acid down my throat & I lost both Carabi & Panagæus!⁸

I was quite astonished to hear of a terrestrial Planaria; for a year or two ago I described in the Annals of N. H. several beautifully coloured terrestrial species of the S. hemisphere, & thought it quite a new fact.⁹ By the way you speak of a sheep with a broken leg not having flukes: I have heard my Father aver that a fever or any serious accident, as broken limb will cause in a man all the intestinal worms to be evacuated; might not this possibly have been the case with the flukes in their early state.¹⁰

I hope you were none the worse for Southampton; I wish I had seen you looking rather fatter: I enjoyed my week extremely & it did me good. I missed you the few last days & we never managed to see much of each other; but there were so many people there, that I for one hardly saw anything of any one.—

Once again thank you very cordially for your kind present & the pleasure it has given me, & believe me | Ever most truly yours | C. Darwin

I have quite forgotten to say how greatly interested I was with your discussion on the statistics of animals: when will Nat: Hist: be so perfect that such points, as you discuss, will be perfectly known about any one animal!¹¹