M Database Inspector (cheetah)
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|05 - Laws of Variation||05-09 - Specific Characters more Variable than Generic Characters||10||
The principle discussed under the last heading may be applied to our present subject. It is notorious that specific characters are more variable than generic.
To explain by a simple example what is meant: if in a large genus of plants some species had blue flowers and some had red, the colour would be only a specific character, and no one would be surprised at one of the blue species varying into red, or conversely; but if all the species had blue flowers, the colour would become a generic character, and its variation would be a more unusual circumstance.
I have chosen this example because the explanation which most naturalists would advance is not here applicable, namely, that specific characters are more variable than generic, because they are taken from parts of less physiological importance than those commonly used for classing genera.
I believe this explanation is partly, yet only indirectly, true; I shall, however, have to return to this point in the chapter on Classification.
It would be almost superfluous to adduce evidence in support of the statement, that ordinary specific characters are more variable than generic; but with respect to important characters I have repeatedly noticed in works on natural history, that when an author remarks with surprise that some important organ or part, which is generally very constant throughout a large group of species, differs considerably in closely-allied species, it is often variable in the individuals of the same species.
And this fact shows that a character, which is generally of generic value, when it sinks in value and becomes only of specific value, often becomes variable, though its physiological importance may remain the same.
Something of the same kind applies to monstrosities: at least Isidore Geoffroy St-Hilaire apparently entertains no doubt that the more an organ normally differs in the different species of the same group, the more subject it is to anomalies in the individuals.
|04 - Natural Selection||04-11 - Divergence of Character||10||
The principle, which I have designated by this term, is of high importance, and explains, as I believe, several important facts.
In the first place, varieties, even strongly-marked ones, though having somewhat of the character of species- as is shown by the hopeless doubts in many cases how to rank them- yet certainly differ far less from each other than do good and distinct species.
Nevertheless, according to my view, varieties are species in the process of formation, or are, as I have called them, incipient species.
How, then, does the lesser difference between varieties become augmented into the greater difference between species?
That this does habitually happen, we must infer from most of the innumerable species throughout nature presenting well-marked differences; whereas varieties, the supposed prototypes and parents of future well-marked species, present slight and ill-defined differences.
Mere chance, as we may call it, might cause one variety to differ in some character from its parents, and the offspring of this variety again to differ from its parent in the very same character and in a greater degree; but this alone would never account for so habitual and large a degree of difference as that between the species of the same genus.
|01 - Variations Under Domestication||01-04 - Inheritance||10||
The results of the various, unknown, or but dimly understood laws of variation are infinitely complex and diversified.
It is well worth while carefully to study the several treatises on some of our old cultivated plants, as on the hyacinth, potato, even the dahlia, &c. and it is really surprising to note the endless points of structure and constitution in which the varieties and sub-varieties differ slightly from each other.
The whole organisation seems to have become plastic, and departs in a slight degree from that of the parental type.
|07 - Instinct||07-01 - Instincts comparable with habits, but different in their origin||10||
The 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 separately, especially as so wonderful an instinct as that of the hive-bee making 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 animals 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 performed 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.
Frederick Cuvier and several of the older metaphysicians have compared instinct with habit.
This comparison gives, I think, a remarkably accurate notion of the frame of mind under which an instinctive action is performed, but not of its origin.
How unconsciously many habitual actions are performed, indeed not rarely in direct opposition to our conscious will! yet they may be modified by the will or reason. Habits easily become associated with other habits, and with certain periods of time and states of the body.
When once acquired, they often remain constant throughout life. Several other points of resemblance between instincts and habits could be pointed out.