Fundamental difficulties and objections-Mr. Herbert Spencer's factors of organic evolution-Disuse and effects of withdrawal of natural selection-Supposed effects of disuse among wild animals-Difficulty as to co-adaptation of parts by variation and selection--Direct action of the environment-The American school of evolutionists-Origin of the feet of the ungulates-Supposed action of animal intelligence— Semper on the direct influence of the environment-Professor Geddes's theory of variation in plants-Objections to the theory-On the origin of spines-Variation and selection overpower the effects of use and disuse-Supposed action of the environment in imitating varia- tions-Weismann's theory of heredity-The cause of variation-The non-heredity of acquired characters-The theory of instinct-Con- General identity of human and animal structure-Rudiments and varia- tions showing relation of man to other mammals-The embryonic development of man and other mammalia-Diseases common to man and the lower animals-The animals most nearly allied to man- The brains of man and apes-External differences of man and apes— Summary of the animal characteristics of man-The geological antiquity of man-The probable birthplace of man-The origin of the moral and intellectual nature of man-The argument from continuity-The origin of the mathematical faculty-The origin of the musical and artistic faculties-Independent proof that these faculties have not been developed by natural selection-The inter- FIG. 20. RECOGNITION OF EDICNEMUS VERMICULATUS AND E. SENEGALENSIS (from Seebohm's Charadriada) PAGE 223 21. RECOGNITION OF CURSORIUS CHALCOPTERUS AND C. GALLICUS (from Seebohm's Charadriado) 224 22. RECOGNITION OF SCOLOPAX MEGALA AND S. STENURA (from Seebohm's Charadriada) 225 23. METHONA PSIDII AND LEPTALIS ORISE. 241 24. OPTHALMIS LINCEA AND ARTAXA SIMULANS (from the Official Narrative of the Voyage of the Challenger) 247 25. WINGS OF ITUNA ILIONE AND THYRIDIA MEGISTO (from Proceedings of the Entomological Society). 251 26. MYGNIMIA AVICULUS AND COLOBORHOMBUS FASCIATIPENNIS 27. MIMICKING INSECTS FROM THE PHILIPPINES (from Semper's Animal Life). 259 260 28. MALVA SYLVESTRIS AND M. ROTUNDIFOLIA (from Lubbock's British Wild Flowers in Relation to Insects) 311 29. LYTHRUM SALICARIA, THREE FORMS OF (from Lubbock's British Wild Flowers in Relation to Insects) 312 30. ORCHIS PYRAMIDALIS (from Darwin's Fertilisation of Orchids). 314 31. HUMMING-BIRD FERTILISING MARCGRAVIA NEPENTHOIDES 320 32. DIAGRAM OF MEAN HEIGHT OF LAND AND DEPTH OF OCEANS 345 33. GEOLOGICAL DEVELOPMENT OF THE HORSE TRIBE (from Huxley's American Addresses) 388 34. DIAGRAM ILLUSTRATING THE GEOLOGICAL DISTRIBUTION OF PLANTS (from Ward's Sketch of Palæobotany). 402 35. TRANSFORMATION OF ARTEMIA SALINA TO A. MILHAUSENII (from Semper's Animal Life) . 426 36. BRANCHIPUS STAGNALIS AND ARTEMIA SALINA (from Semper's Animal Life). 427 37. CHIMPANZEE (TROGLODYTES NIGER) 454 CHAPTER I WHAT ARE SPECIES," AND WHAT IS MEANT BY Definition of species-Special creation-The early Transmutationists— THE title of Mr. Darwin's great work is-On the Origin of The term "species" was thus defined by the celebrated botanist De Candolle: "A species is a collection of all the individuals which resemble each other more than they resemble anything else, which can by mutual fecundation ХХ produce fertile individuals, and which reproduce themselves by generation, in such a manner that we may from analogy suppose them all to have sprung from one single individual." And the zoologist Swainson gives a somewhat similar definition: "A species, in the usual acceptation of the term, is an animal which, in a state of nature, is distinguished by certain peculiarities of form, size, colour, or other circumstances, from another animal. It propagates, 'after its kind,' individuals perfectly resembling the parent; its peculiarities, therefore, are permanent." 1 To illustrate these definitions we will take two common English birds, the rook (Corvus frugilegus) and the crow (Corvus corone). These are distinct species, because, in the first place, they always differ from each other in certain slight peculiarities of structure, form, and habits, and, in the second place, because rooks always produce rooks, and crows produce crows, and they do not interbreed. It was therefore concluded that all the rooks in the world had descended from a single pair of rooks, and the crows in like manner from a single pair of crows, while it was considered impossible that crows could have descended from rooks or vice versâ. The tr origin" of the first pair of each kind was a mystery. Similar remarks may be applied to our two common plants, the sweet violet (Viola odorata) and the dog violet (Viola canina). These also produce their like and never produce each other or intermingle, and they were therefore each supposed to have sprung from a single individual whose origin" was unknown. But besides the crow and the rook there are about thirty other kinds of birds in various parts of the world, all so much like our species that they receive the common name of crows; and some of them differ less from each other than does our crow from our rook. These are all species of the genus Corvus, and were therefore believed to have been always as distinct as they are now, neither more nor less, and to have each descended from one pair of ancestral crows of the same identical species, which themselves had an unknown "origin." Of violets there are more than a hundred different kinds in various parts of the world, all differing very slightly from each other and forming distinct. 1 Geography and Classification of Animals, p. 350. |