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
MISCELLANEOUS OBJECTIONS TO THE THEORY OF NATURAL SELECTION Read More »
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
Chapter 25 And the secret garden bloomed and bloomed and every morning revealed new miracles. In the robin’s nest there were eggs and the robin’s mate sat upon them, keeping them warm with her feathery little breast and careful wings. At first she was very nervous, and the robin himself was indignantly watchful. Even Dickon
Chapter 24 The secret garden was not the only one Dickon worked in. Round the cottage on the moor there was a piece of ground enclosed by a low wall of rough stones. Early in the morning and late in the fading twilight and on all the days Colin and Mary did not see him,
Chapter 23 Dr Craven had been waiting some time at the house when they returned to it. He had indeed begun to wonder if it might not be wise to send someone out to explore the garden paths. When Colin was brought back to his room, the poor man looked him over seriously.“You should not
Chapter 22 When his head was out of sight, Colin turned to Mary.“Go and meet him,” he said, and Mary flew across the grass to the door under the ivy.Dickon was watching him with sharp eyes. There were scarlet spots on his cheeks and he looked amazing, but he showed no signs of falling.“I can