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Show 184 DIFFICULTIES ON THEORY. [CII.A.P. VI. organic beings of the same class, and which is quite independent of their habits of life. On my theory, unity of type is explained by unity of descent. The expression of conditions of existence, so often insisted o.n by the illustrious Cuvier, is fully embraced by the principle of natural selection. . For natural selection acts by either now adapting the varying parts of each being to its organic and inorganic conditions of life; or by having adapted them during long-past periods of time : the adaptations being aided in some_ cases by use and disuse, being slightly affected by the direct action of the external conditions of life, and being in all cases subjected to the several laws of growth. Hence, in fact, the law of the Conditions of Existence is the higher law ; as it includes, through the inheritance of former adaptations, that of Unity of Type. OHA.P, VII.] INSTINCT. 185 CHAPTER VII. INSTINCT. Instincts comparable with habits, but different in their origin-Instincts graduatedAphides and ants-Instincts variable-Domestic instincts, their origin-Natural instincts of the cuckoo, ostrich, and parasitic bees-Slave-making ants-Hive-bee, its cell-making instinct-Difficulties on the theory of the Natural Selection of instincts-Neuter or sterile insects-Summary. TrrE subject of instinct might have been worked into the previous chapters ; but I have thought that it would be more convenient to treat the subject sep'arately, especially as so wonderful an instinct as that of the hive-bee 1naking its cells will probably have occurred to many readers, as a .difficulty sufficient to overthrow my whole theory. I must premise, that I have nothing to do with the origin of the primary mental powers, any more than I have with that of life itself. We are concerned only with the diversities of instinct and of the other mental qualities of aniInals within the same class. I will not attempt any definition of instinct. It would be easy to show that several distinct mental actions are commonly embraced by this term; but every one understands what is meant, when it is said that instinct impels the cuckoo to migrate and to lay her eggs in. other birds' nests. An action, which we ourselves should require experience to enable us to perform, when perfoi·med by an animal, more especially by a very young one, without any experience, and when performed by many individuals in the same way, without their knowing for ·what purpose it is performed, is usually said to be instinctive. But I could show that none of these characters of instinct are universal. A little dose, as Pierre Huber expresses it, of judgment or reason, often comes into play, even in animals very low in the scale of nature. . |