Part I

§ I. [[ON VARIATION UNDER DOMESTICATION, AND ON THE PRINCIPLES OF SELECTION.]]

An individual organism placed under new conditions [often] sometimes varies in a small degree and in very trifling respects such as stature, fatness, sometimes colour, health, habits in animals and probably disposition. Also habits of life develope certain parts. Disuse atrophies. [Most of these slight variations tend to become hereditary.]

When the individual is multiplied for long periods by buds the variation is yet small, though greater and occasionally a single bud or individual departs widely from its type (example)[36] and continues steadily to propagate, by buds, such new kind.

[36] Evidently a memorandum that an example should be given.

When the organism is bred for several generations under new or varying conditions, the variation is greater in amount and endless in kind [especially[37] holds good when individuals have long been exposed to new conditions]. The nature of the external conditions tends to effect some definite change in all or greater part of offspring,--little food, small size--certain foods harmless &c. &c. organs affected and diseases--extent unknown. A certain degree of variation (Müller's twins)[38] seems inevitable effect of process of reproduction. But more important is that simple [[?]] generation, especially under new conditions [when no crossing] [[causes]] infinite variation and not direct effect of external conditions, but only in as much as it affects the reproductive functions[39]. There seems to be no part (beau ideal of liver)[40] of body, internal or external, or mind or habits, or instincts which does not vary in some small degree and [often] some [[?]] to a great amount.

[37] The importance of exposure to new conditions for several generations is insisted on in the Origin, Ed. i. p. 7, also p. 131. In the latter passage the author guards himself against the assumption that variations are "due to chance," and speaks of "our ignorance of the cause of each particular variation." These statements are not always remembered by his critics.

[38] Cf. Origin, Ed. i. p. 10, vi. p. 9, "Young of the same litter, sometimes differ considerably from each other, though both the young and the parents, as Müller has remarked, have apparently been exposed to exactly the same conditions of life."

[39] This is paralleled by the conclusion in the Origin, Ed. i. p. 8, that "the most frequent cause of variability may be attributed to the male and female reproductive elements having been affected prior to the act of conception."

[40] The meaning seems to be that there must be some variability in the liver otherwise anatomists would not speak of the 'beau ideal' of that organ.

[All such] variations [being congenital] or those very slowly acquired of all kinds [decidedly evince a tendency to