Page:The Depths of the Sea - Wyville - 1873.djvu/49

. I.] of peculiar creatures are few, yet sufficient to give a marked character to it, whilst the other portions of its population are derived from the higher zones, and must be regarded as colonists. As we descend deeper and deeper in this region, its inhabitants become more and more modified, and fewer and fewer, indicating our approach towards an abyss where life is either extinguished, or exhibits but a few sparks to mark its lingering presence,"

Forbes pointed out that the groups of animals having their maximum development in these several zones are thoroughly characteristic, and that groups of representative forms occupy the same zones all over the world, so that on examining an assemblage of marine animals from any locality, it is easy to tell from what zone of depth they have been procured. At all periods of the earth's history, there has been the same clear definition of zones of depth, and fossil animals from any particular zone are in some sense representative of the fauna of the corresponding zone at the present day. We can, therefore, usually tell with tolerable certainty to which zone of depth a particular assemblage of fossils is to be referred.

Although we must now greatly modify our views with regard to the extent and fauna of the zone of deep-sea corals, and give up all idea of a zero of animal life, still we must regard Forbes' investigation into the bathymetrical distribution of animals as marking a great advance on previous knowledge. His experience was much wider than that of any other naturalist of his time; the practical difficulties in the way of testing his conclusions were great, and