From Edward Blyth 26 April 1869
21 Chalcot Crescent, | Regent’s Pk,
Dear Mr. Darwin,
I was unable last week to visit the B.M., but I examined the rhesus monkeys at the Gardens, & there is no difference whatever in the amount of extension of the nude face in the two sexes.1 In the females of this group, the sexual organs exhibit an immense development at times, as you cannot but know. In the mandrill & drill, which animals exemplify the culmination of the Macacus & Cercopithecus series, the full grown females are very much smaller than the full-grown males; & in the male mandrill more especially the peculiar characteristics of the series are most highly enhanced; the brilliant colouring of the nude & especially of the sexual organs, most unusual in the class mammalia, but which is also seen in some of the small Cercopitheci.2
That is a capital figure of the musk-deer in last weeks no. of the Illustrated London News, & I furnished the description of it. I have now just written to the editor of that paper, to request him to figure the Abyssinian wart-hog (Phacochœrus Æliani) that has recently arrived, and which is much more different from the Southern species (P. æthiopicus) than I had expected.3 Although a half-grown sow, I can perceive that the curious facial appendages will be much less developed than in the female of the Southern species, and it has immense white whiskers, & very long flowing black hair upon the middle of its back—
Yours very truly, | E Blyth
Has found no difference between male and female rhesus monkeys at the Zoological Gardens in amount of facial hairiness. Observations on other monkeys.