The geographical and geological distribution of animals / by Angelo Heilprin.
- Angelo Heilprin
- Date:
- 1907
Licence: In copyright
Credit: The geographical and geological distribution of animals / by Angelo Heilprin. Source: Wellcome Collection.
24/466 page 6
![camel, gazelle, and ostrich, would present to him certain features of a fauna which was in the main unknown to him; in India the ele- phant, lion, and rhinoceros, and other curious denizens of the jun- gle, the python and crocodile, and the numerous birds of resplendent plumage, would probably crowd from his memory the forms of the creatures ordinarily most familiar to him, and lead a jiassage to the ultimate goal of his journey, Australia, Avhere he would meet with the most singular and most distinctive fauna on the surface of the earth. Much nearer to his northern home—on opposite sides of the JMediterranean—and with much less travelling, the naturalist Avill discern scarcely less Avell-marked faunal dillerences or ])eculiarities. To account for the anomalies which the facts of distribution present is the still unsolved ])roblem that is put before the zoogeographer. Granting, with the doctrine of evolution, that all the complex assemblages of existing animal forms are modified derivatives from ])reviously existing forms, and that these are ultimately to be traced back to some common ancestor, it must of necessity follow that any given fauna will depend for the degree of its peculiarity, whether great or small, upon the amount of modification, relative to any otlier fa>uia, which it will have imdergone. And this modification can be elTectcd in two Avays; by inherent modification of the indi- vidual types composing the fauna, and by intermixture Avith, or immigration from, contiguous or neighbouring faunas. In both cases, manifestly, isolation or its ojiposite, union of habitation, Avill constitute the governing factor in determining the amount of A^aria- tion. A region that is broadly separated from all others Avill, natu- rally, tend to develop a fauna distinct from any other, since the ])rogressive modifications in its constituent faunal elements must ul- timately lead to divergence; and the greater the period of isolation the greater, of necessity, Avill be the amount of this divergence, or the more pronounced the faunal individualisation. Hence it is that in the greater number of the more distantly removed island grou])s, or in those Avliich are separated by more or less im])assable barriers from the nearest land-mass, avc meet Avith such highly specialised faunas. The Galapagos Islands, for example, as will be more fully illustrated farther on, have a fauna very distinct from that of any ]).ut of South America, although removed from it by a distance of less than seven hundred miles. The birds are cpiite distinct, and so are](https://iiif.wellcomecollection.org/image/b29011115_0024.jp2/full/800%2C/0/default.jpg)
