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Prof. Preyer. It seems there are mammae erraticae — so give up Reversion with women

March 24 /69

Descent 1: 125, n38: "In my 'Variation of Animals under Domestication' (vol. ii. p. 57) I attributed the not very rare cases of supernumerary mammæ in women to reversion. I was led to this as a probable conclusion, by the additional mammæ being generally placed symmetrically on the breast, and more especially from one case, in which a single efficient mamma occurred in the inguinal region of a woman, the daughter of another woman with supernumerary mammæ. But Prof. Preyer ('Der Kampf um das Dasein,' 1869, s. 45) states that mammæ erraticæ have been known to occur in other situations, even on the back; so that the force of my argument is greatly weakened or perhaps quite destroyed."