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Utilitarian Doctrine, how far true: Beauty, how acquired.
The foregoing remarks lead me to say a few words on the protest lately made by some naturalists against the utilitarian doctrine that every detail of structure has been produced for the good of its possessor. They believe that many structures have been created...
Reciprocal Dimorphism and Trimorphism.
This subject may be here briefly discussed, and will be found to throw some light on hybridism. Several plants belonging to distinct orders present two forms, which exist in about equal numbers and which differ in no respect except in their reproductive organs...
On the Absence of Numerous Intermediate Varieties in any Single Formation.
From these several considerations it cannot be doubted that the geological record, viewed as a whole, is extremely imperfect; but if we confine our attention to any one formation, it becomes much more difficult to understand why we do not therein find closely ...
On the Poorness of our Palæontological Collections.
Now let us turn to our richest museums, and what a paltry display we behold! That our collections are imperfect is admitted by every one. The remark of that admirable palæontologist, Edward Forbes, should never be forgotten, namely, that very many fossil speci...
On the Lapse of Time, as inferred from the rate of Deposition and extent of Denudatym.
Independently of our not finding fossil remains of such infinitely numerous connecting links, it may be objected that time cannot have sufficed for so great an amount of organic change, all changes having been effected slowly. It is hardly possible for me to r...
On the Absence of Intermediate Varieties at the Present Day.
In the sixth chapter I enumerated the chief objections which might be justly urged against the views maintained in this volume. Most of them have now been discussed. One, namely, the distinctness of specific forms and their not being blended together by innume...
Summary of Chapter.
First crosses between forms, sufficiently distinct to be ranked as species, and their hybrids, are very generally, but not universally, sterile. The sterility is of all degrees, and is often so slight that the most careful experimentalists have arrived at diam...
Hybrids and Mongrels compared, independently of their fertility.
Independently of the question of fertility, the offspring of species and of varieties when crossed may be compared in several other respects. Gärtner, whose strong wish it was to draw a distinct line between species and varieties, could find very few, and, as ...
Fertility of Varieties when Crossed, and of their Mongrel Offspring, not universal.
It may be urged as an overwhelming argument that there must be some essential distinction between species and varieties inasmuch as the latter, however much they may differ from each other in external appearance, cross with perfect facility, and yield perfectl...
Origin and Causes of the Sterility of first Crosses and of Hybrids.
At one time it appeared to me probable, as it has to others, that the sterility of first crosses and of hybrids might have been slowly acquired through the natural selection of slightly lessened degrees of fertility, which, like any other variation, spontaneou...
Summary: The Law of Unity of Type and of the Conditions of Existence embraced by the Theory of Natural Selection.
We have in this chapter discussed some of the difficulties and objections which may be urged against the theory. Many of them are serious; but I think that in the discussion light has been thrown on several facts, which on the belief of independent acts of cre...
Laws governing the Sterility of first Crosses and of Hybrids.
We will now consider a little more in detail the laws governing the sterility of first crosses and of hybrids. Our chief object will be to see whether or not these laws indicate that species have been specially endowed with this quality, in order to prevent th...
Distinction between the Sterility of First Crosses and of Hybrids
The view commonly entertained by naturalists is that species, when intercrossed, have been specially endowed with sterility, in order to prevent their confusion. This view certainly seems at first highly probable, for species living together could hardly have ...
Summary.
I have endeavoured in this chapter briefly to show that the mental qualities of our domestic animals vary, and that the variations are inherited. Still more briefly I have attempted to show that instincts vary slightly in a state of nature. No one will dispute...
Objections to the Theory of Natural Selection as applied to Instincts: Neuter and Sterile Insects.
It has been objected to the foregoing view of the origin of instincts that "the variations of structure and of instinct must have been simultaneous and accurately adjusted to each other, as a modification in the one without an immediate corresponding change in...
Special Instincts.
We shall, perhaps, best understand how instincts in a state of nature have become modified by selection by considering a few cases. I will select only three,— namely, the instinct which leads the cuckoo to lay her eggs in other birds' nests; the slave-making i...
Inherited Changes of Habit or Instinct in Domesticated Animals.
The possibility, or even probability, of inherited variations of instinct in a state of nature will be strengthened by briefly considering a few cases under domestication. We shall thus be enabled to see the part which habit and the selection of so-called spon...
Instincts Comparable with Habits, but Different in Their Origin
Many instincts are so wonderful that their development will probably appear to the reader a difficulty sufficient to overthrow my whole theory. I may here premise, that I have nothing to do with the origin of the mental powers, any more than I have with that o...
Miscellaneous Objections to the Theory of Natural Selection
I will devote this chapter to the consideration of various miscellaneous objections which have been advanced against my views, as some of the previous discussions may thus be made clearer; but it would be useless to discuss all of them, as many have been made ...
On the sudden Appearance of whole Groups of allied Species.
The abrupt manner in which whole groups of species suddenly appear in certain formations, has been urged by several palæontologists — for instance, by Agassiz, Pictet, and Sedgwick — as a fatal objection to the belief in the transmutation of species. If numero...