The American Naturalist, المجلد 46

الغلاف الأمامي
Essex Institute, 1912
 

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مقاطع مشهورة

الصفحة 372 - The cause to which I allude, is the constant tendency in all animated life to increase beyond the nourishment prepared for it.
الصفحة 278 - I HAVE hitherto sometimes spoken as if the variations — so common and multiform in organic beings under domestication, and in a lesser degree in those in a state of nature — had been due to chance. This, of course, is a wholly incorrect expression, but it serves to acknowledge plainly our ignorance of the cause of each particular variation.
الصفحة 253 - The principle formerly alluded to under the term of ANALOGICAL VARIATION has probably in these cases often come into play; that is, the members of the same class, although only distantly allied, have inherited so much in common in their constitution, that they are apt to vary under similar exciting causes in a similar manner; and this would obviously aid in the acquirement through natural selection of parts or organs, strikingly like each other, independently of their direct inheritance from a common...
الصفحة 571 - There are seven windows in the head : two nostrils, two eyes, two ears, and a mouth; so in the heavens there are two favorable stars, two unpropitious, two luminaries, and Mercury alone undecided and indifferent. From which and many other similar phenomena of nature, such as the seven metals, etc., which it were tedious to enumerate, we gather that the number of planets is necessarily seven.
الصفحة 277 - Nature produces those things which, being continually moved by a certain principle contained in themselves, arrive at a certain end."- What this internal moving * principle is remains to be discovered.
الصفحة 189 - So under nature with the nascent giraffe, the individuals which were the highest browsers and were able .during dearths to reach even an inch or two above the others, will often have been preserved; for they will have roamed over the whole country in search of food. That the individuals of the same species often differ slightly in the relative lengths of all their parts may be seen in many works of natural history, in which careful measurements are given. These slight proportional differences, due...
الصفحة 82 - But it will have been otherwise with the nascent giraffe, considering its probable habits of life; for those individuals which had some one part or several parts of their bodies rather more elongated than usual, would generally have survived. These will have intercrossed and left offspring, either inheriting the same bodily peculiarities, or with a tendency to vary again in the same manner; whilst the individuals, less favored in the same respects, will have been the most liable to perish.
الصفحة 372 - The effects of this check on man are more complicated. Impelled to the increase of his species by an equally powerful instinct, reason interrupts his career, and asks him whether he may not 'bring beings into the world for whom he cannot provide the means of support.
الصفحة 372 - Among plants and animals the view of the subject is simple. They are all impelled by a powerful instinct to the increase of their species, and this instinct is interrupted by no reasoning or doubts about providing for their offspring. Wherever therefore there is liberty, the power of increase is exerted, and the superabundant effects are repressed afterwards by want of room and nourishment, which is common to animals and plants, and among animals, by becoming the prey of others.
الصفحة 128 - O unwearied feet, travelling ye know not whither ! Soon, soon, it seems to you, you must come forth on some conspicuous hilltop, and but a little way further, against the setting sun, descry the spires of El Dorado. Little do ye know your own blessedness ; for to travel hopefully is a better thing than to arrive, and the true success is to labour.

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