 The influence of cold, darkness, monotony, and restriction is to limit the direct struggle for existence, and therefore to limit the resultant changes. In general the external conditions most favorable to fish life are to be found in the tropical seas,...  Proceedings of the United States National Museum - Page 104by United States National Museum - 1892 - 16 lehteFull view - About this book
 | Burt Green Wilder - 1893 - 580 lehte
...reefs of the tropics have not ? STATEMENT OF THEORY. For the purpose of this discussion we may assume the derivation of species by means of the various...in the tropics is a struggle between fish and fish, and among the individuals of a very great number of species each one acquiring its own peculiar points... | |
 | 1894 - 904 lehte
...destroy vitality and check self-activity. It is not so in the sea. From conditions otherwise favorable in arctic regions the majority of competitors are excluded by their inability to bear the cold. River life is life in isolation. To aquatic animals river life has the same limitations that island... | |
 | David Starr Jordan - 1907 - 610 lehte
...destroy vitality and check activity. It is not so in the sea. From conditions otherwise favourable in arctic regions the majority of competitors are excluded by their inability to bear the cold. River life is life in isolation. To aquatic animals river life has the same limitations that island... | |
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