. An introduction to zoology : for the use of high schools . erged before the influx of thehigher mammals from Eurasia. The persistence of the Proto-theria and Metatheiia in Australia is similaily to be attributedto its long independi nee from Asia. The fauna of Great Britain, finally, can only be accounted foron the assumption that since the Glacial period it has been en-tirely submerged, raised again, and populated from the main-land, but again submerged before this repopulation could becomecomplete. The freedom of Ireland from reptiles is not to beattributed to any uusuitability of climate,
. An introduction to zoology : for the use of high schools . erged before the influx of thehigher mammals from Eurasia. The persistence of the Proto-theria and Metatheiia in Australia is similaily to be attributedto its long independi nee from Asia. The fauna of Great Britain, finally, can only be accounted foron the assumption that since the Glacial period it has been en-tirely submerged, raised again, and populated from the main-land, but again submerged before this repopulation could becomecomplete. The freedom of Ireland from reptiles is not to beattributed to any uusuitability of climate, V)ut to the fact thatthe channel was not dry land sufficiently long to allow theseforms, which are slow at distributing themselves, to reach it. 16, Such facts lead us to the position that the geography of thepast has had the most important influence on determining thegeographical zoology of the present. Each species has a certainarea of distribution, which is called its habitat : it tends towiden this area, as far as the conditions of existence will per-. HIGH SCHOOL ZOOLOGY. 281 mit, but the most effectual barriers are high niountain-cliainsand deep seas. By mapping out the ranges of different speciesit is jiossible to mark out certain zoogeographical regions inwhich the simultaneous occuri-ence of the same or nearly alliedspecies confers a certain similarity of appearance or facies to thefauna. A glance at these regions, as laid down by Dr. Wallacein the accompanying map, will shew that they agree prettywell with our ordinary geographical divisions, except that greatnatural barriers cut off the Ethiopian region from North Africa,the Oiiental from the Palsearctic, and the Australian from theOriental ; these are the Sahara, the Himalaya, and the verydeep sea along Wallaces line, between Bali and Lombok,Boineo and Celebes. This is certainly a most instructiveillustration of the effect of a deep-sea barriei, and of the factthat mere climate does not determine geographical distr
Size: 1224px × 2041px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, booksubjectzoology, bookyear1889
