VII. 3 

 DISPERSAL ,OF ANIMALS 



DISTINCT from the potentialities of increase with which 

 civilization has endowed animal life are the means of dispersal 

 which man has provided in preparing for his own transport. 



The opening of through waterways has been found, for 

 example in Canada, to give to the fishes and the small in- 

 habitants of the waters, access to areas from which they 

 were formerly absent. In 1874 Professor Marsh stated 

 that the Erie Canal, in spite of its length of 360 miles and 

 its ascending and descending locks in both directions, had 

 caused the commingling of the freshwater fishes and the 

 native plants of the Hudson and of the Upper Lakes, so 

 that the fauna and flora of these regions had more species 

 in common than they had before the canal was opened. 

 Just so it is possible that the Panama Canal may for the 

 first time bring inhabitants of the East and West to meet ; 

 and so the great waterway of Scotland, the Caledonian 

 Canal, by connecting the lochs of the Great Glen, and 

 by affording a constant circulation of water owing to the 

 passing of vessels and the inflowing and outflowing to and 

 from the locks, has brought about a commingling of the 

 minute but distinct members of the faunas of the lochs. The 

 body of water which passes from Loch Oich through the 

 Canal into Loch Lochy certainly carries with it from one loch 

 to the other some of the Entomostraca or lower crustaceans 

 (Water-Fleas and the like), as well as other minute organisms 

 which people the water in their thousands. 



Closely associated with the movements of the waters is 

 the influence of the shipping which passes upon their surface, 

 for though there is little scope for transference of animals 

 by such means within the bounds of Scotland, yet we have 

 seen that steamers and the flotsam and jetsam of civilization 

 played a great part in conveying the Colorado Beetle from 

 the United States to Canada across the Detroit River and the 

 breadth of Lake Erie. And it is self-evident that these aliens, 



