60 EVOLUTION [CHAP. II 



Letter 25 going to write will be absolutely superfluous, 1 but I have 

 derived such infinitely great advantage from my new simple 

 microscope, in comparison with the one which I used on 

 board the Beagle, and which was recommended to me by 

 R. Brown, 2 that I cannot forego the mere chance of advantage 

 of urging this on you. The leading point of difference 

 consists simply in having the stage for saucers very large 

 and fixed. Mine will hold a saucer three inches in inside 

 diameter. I have never seen such a microscope as mine, 

 though Chevalier's (from whose plan many points of mine 

 are taken), of Paris, approaches it pretty closely. I fully 

 appreciate the utter absurdity of my giving you advice 

 about means of dissecting ; but I have appreciated myself 

 the enormous disadvantage of having worked with a bad 

 instrument, though thought a few years since the best. 

 Please to observe that without you call especial attention to 

 this point, those ignorant of Natural History will be sure to 

 get one of the fiddling instruments sold in shops. If you 

 thought fit, I would point out the differences, which, from my 

 experience, make a useful microscope for the kind of dis- 

 section of the invertebrates which a person would be likely 

 to attempt on board a vessel. But pray again believe that I 

 feel the absurdity of this letter, and I write merely from the 

 chance of yourself, possessing great skill and having worked 

 with good instruments, [not being] possibly fully aware what 

 an astonishing difference the kind of microscope makes for 

 those who have not been trained in skill for dissection under 

 water. When next I come to town (I was prevented last 

 time by illness) I must call on you, and report, for my own 

 satisfaction, a really (I think) curious point I have made 



this field have stood the test of investigation :"...! am not sure that 

 any one but the historian of anatomical science is ever likely to recur 

 to them, and considering Owen's great capacity, extensive learning, and 

 tireless industry, that seems a singular result of years of strenuous 

 labour." 



1 The results of Mr. Darwin's experience given in the above letter 

 were embodied by Prof. Owen in the section " On the Use of the Micro- 

 scope on Board Ship," forming part of the article "Zoology" in the 

 Manual of Scientific Enquiry, Prepared for the Use of Her Majesty's 

 Navy (London, 1849). 



2 Life and Letters, I., p. 145. 



