THE FRESH WATERS 141 
to be where they are now? To answer this 
very reasonable question briefly is not possible, 
but part of the answer may be given. Among 
the first animals to have bodies—namely, the 
Sponges—we find one family in the fresh 
waters, and all the rest—including many hun- 
dreds of different kinds—in the sea. That is 
a straw which shows how the wind blew. 
Among the Stinging Animals which come 
next in order—the sea-anemones and corals, 
the jelly-fishes and zoophytes—only about half 
a dozen are found in the fresh waters; all the 
rest—thousands of different kinds—live in the 
sea. So in many other cases, and the home of 
the great majority of any great race of animals 
is likely to be the original home of the race. 
Another step in the argument is the Natural 
History rule that when an animal has more 
than one habitat in the course of its life-history, 
the one in which itstarts another generation, or 
begins its own life, is wswa//y the original home. 
The robber-crab wanders far from the shore 
and even climbs the hills, but it goes back to 
the seashore every year to spawn, and there is 
no doubt at all that it was originally a shore 
animal. So the fresh-water eel goes to the deep 
sea to spawn, and there is almost no doubt that 
