The origin of species by means of natural selection, or, The preservation of favoured races in the struggle for life / by Charles Darwin.

Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: The origin of species by means of natural selection, or, The preservation of favoured races in the struggle for life / by Charles Darwin. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    %,■, .Ss*. iar lanuer ' ^ Jsestren), j.U^era- •*iT“ cit re^,be ^Isis* ^s^eretoact unif Ma)' individuals. i., --“‘“'-wastJieconipleT ^vanably follow fe r from tie -V -“vn j !°n a gall-producing insect, 3ns migU result in the case of ie nature of the sap. more common result of changed ;y, and has probably played a ioa of our domestic races, ffe Hess slight peci une species, 3 occa- une litter, and in seedlings i intervals of time, out o io strongly pwo I jt**1*© ■ * 11* slieht or strong ffi&ew*! ****&» *<> indno^'^nae111 i?ed Chap. I. ] VARIATION UNDER DOMESTICATION. the conditions, and partly from the similarity, as Kolreuter and others have remarked, between the variability which follows from the crossing of distinct species, and that which may be observed with plants and animals when reared under new or unnatural con- ditions. Many facts clearly show how eminently susceptible the reproductive system is to very slight changes in the surrounding conditions. Nothing is more easy than to tame an animal, and few things more difficult than to get it to breed freely under confine- ment, even when the male and female unite. How many animals there are which will not breed, though kept in an almost free state in their native country! This is generally, but erroneously, attributed to vitiated instincts. Many cultivated plants display the utmost vigour, and yet rarely or never seed! In some few cases it has been discovered that a very trifling change, such as a little more or less water at some particular period of growth, will determine whether or not a plant will produce seeds. I cannot here give the details which I have collected and elsewhere published on this curious subject; but to show how singular the laws are which determine the reproduction of animals under confinement, I may mention that carnivorous animals, even from the tropics, breed in this country pretty freely under confinement, with the exception of the plantigrades or bear family, which seldom produce young ; whereas carnivorous birds, with the rarest exceptions, hardly ever lay fertile eggs. Many exotic plants have pollen utterly worthless, in the same condition as in the most sterile hybrids. When, on the one hand, we see domesticated animals and plants, though often weak and sickly, breeding freely under confinement; and when, on the other hand, we see individuals, though taken young from a state of nature perfectly tamed, long-lived and healthy (of which I could give numerous instances), yet having their reproductive system so seriously affected by unperceived causes as to fail to act, we need not be surprised at this system, when it does act under confinement, acting irregularly, and producing offspring somewhat unlike their parents. I may add, that as some organisms breed freely under the most unnatural conditions (for instance, rabbits and ferrets kept in hutches), showing that their reproductive organs are not easily affected ; so will some animals and plants withstand domestication or cultivation, and vary very slightly— perhaps hardly more than in a state of nature. Some naturalists have maintained that all variations are con- nected with the act of sexual reproduction ; but this is certainly an error ; for I have given in another work a long list of “sporting plants,” as they are called by gardeners that is, of plants which have suddenly produced a single bud with a new and sometimes widely different character from that of the other buds on the same plant. These bud-variations, as they may be named, can be pro-