Show THE GLACIAL L EPOCH J CONCLUDED i i This astronomical theory is an ingenious ingeni ingeni- ous one but it is purely speculative in its c nature as no observed facts have yet been found to prove its correctness The elevation elevation ele ele- theory independent of the astronomical astronomical astronomical astro- astro explains the greatest number of i. i known wn facts and is therefore now generally generally generally gener gener- ally accepted This epoch had a very marked effect on the distribution of plant and animal life over the surface surface e of the earth The species from that time to the present have undergone but very little change and the geographical distribution then made remains remains re- re mains in a general way to this day During the latter part of last century naturalists naturalists naturalists na na- discovered that many species of the flora of the Alps are aie almost identical to the Arctic flora of both continents and during the present century Arctic species similar to those those found found on the Alps were found on the high mountains of New Hampshire and Colorado Such similar- similar ties were not found to subsist between the flora gi growing owing on the lowlands of the two continents though latter investigations according to Asa As Gray Gray- have proved that greater similarities exist than was formerly supposed To account for the strange distribution of Arctic life naturalists naturalists naturalists first advanced the theory that the same species were independently created in the different localities But as the study of the science of geology advanced this theory gave way to a simpler one Agassiz the eminent scientist about fifty y years ago first called the attention of naturalists naturalists na na naturalists to the glacial epoch a as s affording the most probable explanation of the distribution distribution distribution dis dis- of species During the epochs immediately preceding the glacial the climate climate climate cli cli- mate on the borders of the Arctic ocean was much warmer than it is now Species Species Species cies of fossil plants have been found in inthe inthe inthe the deposits of those epochs on Greenland that now grow groy only in the warm and moist climate of Florida and Louisiana The warm climate and the proximity of the two continents at Behring Bearing sea offered a favorable highway for migration and commingling of species Thus we see he cause of the similarity of the fauna and flora in the polar regions of both continents The question now comes up From where came canie the modern Arctic life if f the fauna and flora of the polar regions previous previous ous to the glacial epoch were tropical or tropical sub-tropical in their nature From the standpoint of the evolutionist the answer is is very simple and comprehensive Variation Variation Vari Vari- yari atio jn in form and structure and the survival survival survival val of the fittest during long ages determined determined deter deter- mined what species should remain in the arctic zone under the changed conditions and what species would have to migrate south or or- else perish Those species that could adapt themselves to the gradually increasing cold would remain on the Arctic shores as long as they were free from ic icat ice at least during a portion of the year and those species that could not th thus lS adapt themselves ves were forced to migrate As the cold gradually increased and the accumulated accumulated accumulated ac ac- cumulated ice moved southward the plant and animal life was crowded further and further south and when the maximum cold was reached the Arctic fauna and flora flourished on the lowlands of the temperate and even tropical sub-tropical zones on both continents The indigenous life was forced to move further urther south where the temperature was not affected with cold and those species growing on the high mountains in the temperate zone were forced down into the valleys to mingle I L. L there with the Arctic species As the cold slowly diminished and the ice began hegan to retreat the Arctic fauna and flora was given two alternatives either to follow the retreating ice to the polar regions regions regions re re- gions or which was the same thing with respect to external conditions to follow the ice retreating up the slopes of the high mountains The majority followed the former course but a large number of species species species cies of both animals and plants took the latter and nd when the earths earth's tern temperature t attained its normal condition those which t a had sought the mountains were cut off as stragglers from their native northern I home by the impassable barriers barrien of intervening intervening intervening inter- inter interI I valleys The plants and animals that had been forced to migrate migrate from from the I temperate and tropical zones into the the southern hemisphere returned and the animal animal an an- imal and vegetable kingdoms were left distributed as we now generally find them J. 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