{21} _J. Linn. Soc. Zool._ iii. p. 45.

The back of this "useless" page is of some interest, although it does
not bear on the question of date,--the matter immediately before us.

It seems to be an outline of the Essay or sketch of 1842, consisting of
the titles of the three chapters of which it was to have consisted.

"I. The Principles of Var. in domestic organisms.

"II. The possible and probable application of these same principles to
wild animals and consequently the possible and probable production of
wild races, analogous to the domestic ones of plants and animals.

"III. The reasons for and against believing that such races have really
been produced, forming what are called species."

It will be seen that Chapter III as originally designed corresponds to
Part II (p. 22) of the Essay of 1842, which is (p. 7) defined by the
author as discussing "whether the characters and relations of animated
things are such as favour the idea of wild species being races descended
from a common stock." Again at p. 23 the author asks "What then is the
evidence in favour of it (the theory of descent) and what the evidence
against it." The generalised section of his Essay having been originally
Chapter III{22} accounts for the curious error which occurs in pp. 18
and 22 where the second Part of the Essay is called Part III.

{22} It is evident that _Parts_ and _Chapters_ were to some extent
interchangeable in the author's mind, for p. 1 (of the MS. we have
been discussing) is headed in ink Chapter I, and afterwards altered
in pencil to Part I.

The division of the Essay into two parts is maintained in the enlarged
Essay of 1844, in which he writes: "The Second Part of this work is
devoted to the general consideration of how far the general economy of
nature justifies or opposes the belief that related species and genera
are descended from common stocks." The _Origin of Species_ however is
not so divided.

We may now return to the question of the date of the Essay. I have found
additional evidence in favour of 1842 in a sentence written on the back
of the Table of Contents of the 1844 MS.--not the copied version but the
original in my father's writing: "This was written and enlarged from a
sketch in 37 pages{23} in Pencil (the latter written in summer of 1842
at Maer and Shrewsbury) in beginning of 1844, and finished it <_sic_> in
July; and finally corrected the copy by Mr Fletcher in the last week i