To W. D. Fox 16 April 
Down Bromley Kent
My dear Fox
I want you to observe one point for me, on which I am extremely much interested & which will give you no trouble beyond keeping your eyes open, & that is a habit I know full well that you have.
I find Horses of various colours often have a spinal band or stripe of different & darker tint than rest of body—rarely transverse bars on legs, generally on under side of front legs—still more rarely a very faint transverse shoulder stripe, like an ass.—
Is there any breed of Delamere Forest Ponies.—1 I have found out little about Ponies in these respects. Sir P. Egerton has, I believe, some quite thorough bred Chesnut horses:2 have any of these the spinal stripe. Mouse-coloured ponies or rather small horses, often have spinal & leg bars. So have Dun Horses (by Dun I mean real colour of cream mixed with brown bay or chesnut).— So have sometimes Chesnuts, but I have not yet got case of spinal stripe in Chesnut Race Horse, or in quite heavy Cart-Horse.—3 Any facts of this nature of such stripes in Horses would be most useful to me.— There is parallel case in legs of Donkey & I have collected some most curious cases of stripes appearing in various crossed equine animals.—4
I have, also, large mass of parallel facts in the breeds of Pigeons about the wing-bars.—5 I suspect it will throw light on colour of primeval Horse. So do help me if occasion turns up.— I have not yet returned your Oology, though I have finished with it; for I have not been in London since, & I did not like to intrust it to Carrier; though perhaps I had now better do so.—6 My health has been lately very bad from overwork & on Tuesday I go for fortnights Hydropathy.7 My work is everlasting.
Farewell— My dear Fox, I trust you are well | Farewell | C. Darwin
Asks WDF for facts about stripes in horses and ponies.
Health has been very bad.