Journal of the Proceedings of the Linnean Society: Zoology

Лицевая обложка
The Society, 1859
 

Отзывы - Написать отзыв

Не удалось найти ни одного отзыва.

Другие издания - Просмотреть все

Часто встречающиеся слова и выражения

Популярные отрывки

Стр. 57 - ... become altogether extinct. Between these extremes the species will present various degrees of capacity for ensuring the means of preserving life; and it is thus we account for the abundance or rarity of species. Our ignorance will generally prevent us from accurately tracing the effects to their causes; but could we become perfectly acquainted with the organization and habits of the various species of animals, and could we measure the capacity of each for performing the different acts necessary...
Стр. 46 - On the Variation of Organic Beings in a state of Nature ; on the Natural Means of Selection ; on the Comparison of Domestic Races and true Species.
Стр. 60 - We see, then, that no inferences as to varieties in a state of nature can be deduced from the observation of those occurring among domestic animals. The two are so much opposed to each other in every circumstance of their existence, that what applies to the one is almost sure not to apply to the other.
Стр. 209 - The year which has passed . . . has not indeed, been marked by any of those striking discoveries which at once revolutionize, so to speak, the department of science on which they bear...
Стр. 51 - I have found it hard constantly to bear in mind that the increase of every single species is checked during some part of its life, or during some shortly recurrent generation. Only a few of those annually born can live to propagate their kind. What a trifling difference must often determine which shall survive and which perish.
Стр. 51 - I think it can be shown that changed conditions of existence is the main cause of the child not exactly resembling its parents; and in nature geology shows us what changes have taken place, and are taking place. We have almost unlimited time; no one but a practical geologist can fully appreciate this. Think of the Glacial period, during the whole of which the same species at least of shells have existed; there must have been during this period millions on millions of generations.
Стр. 58 - These results must follow as surely as old age, intemperance, or scarcity of food produce an increased mortality. In both cases there may be many individual exceptions; but on the average the rule will invariably be found to hold good. All varieties will therefore fall into two...
Стр. 59 - ... of form, any of which, tending to increase the facilities for preserving existence, must by the same general law, in their turn become predominant. Here, then, we have progression and continued divergence deduced from the general laws which regulate the existence of animals in a state of nature, and from the undisputed fact that varieties do frequently occur. It is not, however, contended that this result would be invariable; a change of physical conditions in the district might at times materially...
Стр. 57 - ... that the comparative abundance or scarcity of the individuals of the several species is entirely due to their organization and resulting habits, which, rendering it more difficult to procure a regular supply of food and to provide for their personal safety in some cases than in others, can only be balanced by a difference in the population which have to exist in a given area...
Стр. 59 - Now the scale on which nature works is so vast — the numbers of individuals and periods of time with which she deals approach so near to infinity, that any cause, however slight, and however liable to be veiled and counteracted by accidental circumstances, must in the end produce its full legitimate results.

Библиографические данные