The Origin of Species

Introduction

p vi

The natural selection of those individuals most fitted to their environment is a truism, especially when expressed in its inverted form as 'the survival of the fittest', a phrase first used by Herbert Spencer. As early as 1831, the importance of natural selection had been pointed out by Patrick Matthew [...]

An Historical Sketch of the progress of opinion on the origin of species, previously to the publication of the first edition of this work

[...] it is quite immaterial whether or not Professor Owen preceded me, for both of us, as shown in this historical sketch, were long ago preceded by Dr. Wells and Mr. Matthews.

Chapter II – Variation Under Nature

Doubful Species

[...] no observer can determine for another, even if he can do it for himself, which of these Phytophagic forms ought to be called species and which varieties. Mr. Walsh ranks the forms which it may be supposed would freely intercross, as varieties; and those which appear to have lost this power, as species.

Chapter IV – Natural Selection; or the Survival of the Fittest

I mean by Nature, only the aggregate action and product of many natural laws, and by laws the sequence of events as ascertained by us.

Sexual Selection

Divergence of Character

On the Degree to which Organisation tends to advance

In some cases, as we shall hereafter see, lowly organized forms appear to have been preserved to the present day, from inhabiting confined or peculiar stations, where they have been subjected to less severe competition, and where their scanty numbers have retarded the chance of favourable variations arising.

Chapter VI – Difficulties of the Theory

Modes of Transition

All physiologists admit that the swimbladder is homologous, or "ideally similar" in position and structure with the lungs of the higher vertebrate animals: hence there is no reason to doubt that the swimbladder has actually been converted into lungs, or an organ used exclusively for respiration.

We can thus [...] understand the strange fact that every particle of food which we swallow has to pass over the orifice of the trachea, with some risk of falling into the lungs, notwithstanding the beautiful contrivance by which the glottis is closed.

Special Difficulties of the Theory of Natural Selection

Hence in the several fishes furnished with electric organs, these cannot be seen as homologous, but only as analogous in function.

Chapter VIII – Instinct

Objections to the Theory of Natural Selection as applied to Instinct: Neuter and Sterile Insects

I am surprised that no one has hitherto advanced this demonstrative case of neuter insects against the well-known doctrine of inherited habits, as advanced by Lamarck.

Chapter XIV – Mutual Affinities of Organic Beings: Morphology: Embryology: Rudimentary Organs

Classification

From the most remote periods in the history of the world organic beings have been found to resemble each other in descending degrees, so that they can be classed in groups under groups. This classification is not arbitrary like the grouping of stars in constellations.

Expressions such as that famous one by Linn�us, which we often meet with in a more or less concealed form, namely, that the characters do not make the genus, but that the genus gives the characters seems to imply that some deeper bond is included in our classifications than mere resemblance. I believe that this is the case, and that community of descent—the one known cause of close similarity in organic beings—is the bond [...]

Analogical Resemblances

[...] in some districts of South America, where, for instance, an Ithomia abounds in gaudy swarms, another butterfly, namely a Leptalis, is often found mingled in the same flock; and the latter so closely resembles the Ithomia in every shade and stripe of colour and even in the shape of its wings, that Mr. Bates, with his eyes sharpened by collecting during eleven years, was, though always on his guard, continually deceived.

On the Nature of the Affinities connecting Organic Beings

[...] the fact is striking that the discovery of Australia has not added an insect belonging to a new class; and that in the vegetable kingdom [...], it has added only two or three families of small sizes.

Chapter XV – Recapitulation and Conclusion

Flowers and fruit have been rendered conspicuous by brilliant colours in contrast with the green foliage, in order that the flowers may be easily seen, visited, and fertilised by insects, and the seeds disseminated by birds. How it comes that certains colours, sounds, and forms should give pleasure to man and the lower animals,—that is, how the sense of beauty in its simplest form was first acquired,—we do not know any more than how certain odours and flavours were first rendered agreeable.

Who can explain what is the essence of the attraction of gravity? No one now objects to following out the results consequent on this unknown element of attraction; notwithstanding that Leibniz formerly accused Newton of introducing "occult qualities and miracles into philosophy".

[...] we shall at least be freed from the vain search for the undiscovered and undiscoverable essence of the term species.