CHAPTER XIII Distribution of fresh-water productions – On the inhabitants of oceanic islands – Absence of batrachians and of terrestrial mammals – On the relation of the inhabitants of islands to those of the nearest mainland – On colonisation from the nearest source with subsequent modification – Summary of the last and present chapter. Fresh-water […]
CHAPTER XII Present distribution cannot be accounted for by differences in physical conditions – Importance of barriers – Affinity of the productions of the same continent – Centres of creation – Means of dispersal, by changes of climate and of the level of the land, and by occasional means – Dispersal during the Glacial period*
CHAPTER XI On the slow and successive appearance of new species – On their different rates of change – Species once lost do not reappear – Groups of species follow the same general rules in their appearance and disappearance as do single species – On extinction – On simultaneous changes in the forms of life
CHAPTER X On the absence of intermediate varieties at the present day – On the nature of extinct intermediate varieties; on their number – On the lapse of time, as inferred from the rate of denudation and of deposition – On the lapse of time as estimated by years – On the poorness of our
CHAPTER IX Distinction between the sterility of first crosses and of hybrids – Sterility various in degree, not universal, affected by close interbreeding, removed by domestication – Laws governing the sterility of hybrids – Sterility not a special endowment, but incidental on other differences, not accumulated by natural selection – Causes of the sterility of
CHAPTER VIII Instincts comparable with habits, but different in their origin – Instincts graduated – Aphides and ants – Instincts variable – Domestic instincts, their origin – Natural instincts of the cuckoo, molothrus, ostrich, and parasitic bees – Slave-making ants – Hive-bee, its cell-making instinct – Changes of instinct and structure not necessarily simultaneous –
CHAPTER VII Longevity – Modifications not necessarily simultaneous – Modifications apparently of no direct service – Progressive development – Characters of small functional importance, the most constant – Supposed incompetence of natural selection to account for the incipient stages of useful structures – Causes which interfere with the acquisition through natural selection of useful structures
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CHAPTER VI Difficulties of the theory of descent with modification – Absence or rarity of transitional varieties – Transitions in habits of life – Diversified habits in the same species – Species with habits widely different from those of their allies – Organs of extreme perfection – Modes of transition – Cases of difficulty –
CHAPTER V Effects of changed conditions – Use and disuse, combined with natural selection; organs of flight and of vision – Acclimatisation – Correlated variation – Compensation and economy of growth – False correlations – Multiple, rudimentary, and lowly organised structures variable – Parts developed in an unusual manner are highly variable; specific characters more
CHAPTER IV Natural Selection – its power compared with man’s selection – its power on characters of trifling importance – its power at all ages and on both sexes – Sexual selection – On the generality of intercrosses between individuals of the same species – Circumstances favourable and unfavourable to the results of Natural Selection,
NATURAL SELECTION; OR THE SURVIVAL OF THE FITTEST Read More »
CHAPTER III Its bearing on natural selection – The term used in a wide sense – Geometrical ratio of increase – Rapid increase of naturalized animals and plants – Nature of the checks to increase – Competition universal – Effects of climate – Protection from the number of individuals – Complex relations of all animals
CHAPTER II Variability – Individual differences – Doubtful species – Wide ranging, much diffused, and common species, vary most – Species of the larger genera in each country vary more frequently than the species of the smaller genera – Many of the species of the larger genera resemble varieties in being very closely, but unequally,
CHAPTER I Causes of variability – Effects of habit and the use or disuse of parts – Correlated variation – Inheritance – Character of domestic varieties – Difficulty of distinguishing between varieties and species – Origin of domestic varieties from one or more species – Domestic pigeons, their differences and origin – Principles of selection,
Chapter 27 In each century since the beginning of the world wonderful things have been discovered. In the last century more amazing things were found out than in any century before. In this new century hundreds of things still more astounding will be brought to light. At first people refuse to believe that a strange
Chapter 26 Their belief in the Magic was an abiding thing. After the morning’s incantations Colin sometimes gave them Magic lectures.“I like to do it,” he explained, “because when I grow up and make great scientific discoveries I shall be obliged to lecture about them, and so this is practice. I can only give short