{301} <Note in original.> Is this the Galeopithecus? I forget. <_Galeopithecus_ "or the flying Lemur" is mentioned in the corresponding discussion in the _Origin_, Ed. i. p. 181, vi. p. 217, as formerly placed among the bats. I do not know why it is described as partly aquatic in its habits.> {302} In the _Origin_, Ed. vi. p. 221, the author modified the statement that it _never_ climbs trees; he also inserted a sentence quoting Mr Hudson to the effect that in other districts this woodpecker climbs trees and bores holes. See Mr Darwin's paper, _Zoolog. Soc. Proc._, 1870, and _Life and Letters_, iii. p. 153. {303} Note by the late Alfred Newton. Richardson in _Fauna Boreali-Americana_, i. p. 49. {304} <Note in original.> See Richardson a far better case of a polecat animal <_Mustela vison_>, which half-year is aquatic. <Mentioned in _Origin_, Ed. i. p. 179, vi. p. 216.> PART II{305} ON THE EVIDENCE FAVOURABLE AND OPPOSED TO THE VIEW THAT SPECIES ARE NATURALLY FORMED RACES, DESCENDED FROM COMMON STOCKS {305} In the _Origin_ the division of the work into Parts I and II is omitted. In the MS. the chapters of Part II are numbered afresh, the present being Ch. I of Pt. II. I have thought it best to call it Ch. IV and there is evidence that Darwin had some thought of doing the same. It corresponds to Ch. IX of _Origin_, Ed. i., Ch. X in Ed. vi. CHAPTER IV ON THE NUMBER OF INTERMEDIATE FORMS REQUIRED ON THE THEORY OF COMMON DESCENT; AND ON THEIR ABSENCE IN A FOSSIL STATE