To John Davy 26 March 
Down Farnborough Kent
My dear Sir
I have just read your Paper: it seem to me most interesting & curious. How admirably you have diversified your experiments! I will send it today to the Royal Socy., & will ask for an acknowledgment to be sure that it arrives safely.—1
The case of the ovum exposed on the moss for three days, & the wonderful retention of vitality of the ova in very moist air seem of particular value in regard to the power of dispersal. Surely these results will, also, be of practical value.—
Hardly anything has surprised me more than the non-developed ova having less tenacity of life than those much more fully developed.— I almost hope that shd. you ever have another opportunity, it may seem to you worth while to test this one point again.—2
I have been much struck by your experiments on the effect of rather high temperatures; I had often speculated whether the ova accidentally introduced into the stomach of an herbivorous bird could escape the action of its gastric juice, but I had not at all calculated on the very injurious action of the mere temperature.—
With many such experiments as yours, Geographical Distribution would become in my opinion, a very different subject to what it is now. Allow me again to thank you for the great interest I have received from your Memoir & for the honour you have done me.
Pray believe me | Yours truly obliged | Charles Darwin
Discusses JD’s paper ["On ova of salmon"]. His experiments are of particular value regarding power of dispersal and geographical distribution and would make of them a very different subject. Hopes JD can test again the tenacity of life of non-developed ova being less than that of those fully developed – a result which surprised CD.