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Cuttle-Fish

Skeleton of Ichthyosaurus

Cytheridea Torosa (from Messrs. Brady and Robertson's paper in
Ann. and Mag. of Nat. Hist., 1870)

A Polyzoon, with Bird's-head processes
Bird's-head processes greatly enlarged

Antechinus Minutissimus and Mus Delicatulus (from Mr. Andrew
Murray's "Geographical Distribution of Mammals")
Outlines of Wings of Butterflies of Celebes compared with those of
allied species elsewhere
Great Shielded Grasshopper

The Six-shafted Bird of Paradise

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(The above seven figures are from Mr. A. Wallace's " Malay
Archipelago.")

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Much enlarged horizontal Section of the Tooth of a Labyrinthodon (from Professor Owen's "Odontography")

Hand of the Potto (from life)

Skeleton of the Plesiosaurus

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The Aye-Aye (from Trans. of Zool. Soc.)

Dentition of Sabre-toothed Tiger (from Professor Owen's

graphy")

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84, 160

88, 120, 149, 199

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Trilobite

Inner side of Lower Jaw of Pleurodont Lizard (from Professor
Owen's "Odontography")

Solenoden (from Berlin Trans.)

Tarsal Bones of Galago and Cheirogaleus (from Proc. Zool. Soc.)

Squilla

Parts of the Skeleton of the Lobster

Odonto

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iii., 119

120, 150, 201

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125

152, 193

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183

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190, 241

ii., 196

197

Spine of Galago Allenii (from Proc. Zool. Soc.)
Vertebræ of Axolotl (from Proc. Zool. Soc.)...
Annelid undergoing spontaneous fission
Aard-Vark (Orycteropus capensis)

Pangolin (Manis)

Skeleton of Manus and Pes of a Tailed Batrachian (from Professor
Gegenbaur's "Tarsus und Carpus”)

Flexor Muscles of Hand of Nycticebus (from Proc. Zool. Soc.)

The Fibres of Corti

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THE GENESIS OF SPECIES.

CHAPTER I.

INTRODUCTORY.

The problem of the genesis of species stated.-Nature of its probable solution.-Importance of the question.-Position here defended.— Statement of the DARWINIAN THEORY.-Its applicability to details of geographical distribution; to rudimentary structures; to homology; to mimicry, &c.-Consequent utility of the theory.-Its wide acceptance. -Reasons for this, other than, and in addition to, its scientific value.Its simplicity. Its bearing on religious questions.—Odium theologicum and odium antitheologicum.—The antagonism supposed by many to exist between it and theology neither necessary nor universal.Christian authorities in favour of evolution. -Mr. Darwin's "Animals and Plants under Domestication."-Difficulties of the Darwinian theory enumerated.

THE great problem which has so long exercised the minds of naturalists, namely, that concerning the origin of different kinds of animals and plants, seems at last to be fairly on the road to receive-perhaps at no very distant future-as satisfactory a solution as it can well have.

But the problem presents peculiar difficulties. The birth of a "species" has often been compared with that of an individual." The origin, however, of even an individual animal or plant (that which determines an embryo to

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evolve itself,-as, e.g., a spider rather than a beetle, a rose-plant rather than a pear) is shrouded in obscurity. A fortiori must this be the case with the origin of a "species."

Moreover, the analogy between a "species" and an "individual" is a very incomplete one. The word "individual" denotes a concrete whole with a real, separate, and distinct existence. The word "species," on the other hand, denotes a peculiar congeries of characters, innate powers and qualities, and a certain nature realized indeed in individuals, but having no separate existence, except ideally as a thought in some mind.

Thus the birth of a "species" can only be compared metaphorically, and very imperfectly, with that of an "individual."

Individuals as individuals, actually and directly produce and bring forth other individuals; but no "congeries of characters," no common nature" as such, can directly bring forth another "common nature," because, per se, it has no existence (other than ideal) apart from the individuals in which it is manifested.

The problem then is, " by what combination of natural laws does a new common nature' appear upon the scene of realized existence?" .e. how is an individual embodying such new characters produced?

For the approximation we have of late made towards the solution of this problem, we are mainly indebted to the invaluable labours and active brains of Charles Darwin and Alfred Wallace.

Nevertheless, important as have been the impulse and direction given by those writers to both our observations and speculations, the solution will not (if the views here.

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