The same
agency may have come into play with the eggs of some of the smaller
fresh-water animals.
Other and unknown agencies probably have also played a part. I have stated
that fresh-water fish eat some kinds of seeds, though they reject many
other kinds after having swallowed them; even small fish swallow seeds of
moderate size, as of the yellow water-lily and Potamogeton. Herons and
other birds, century after century, have gone on daily devouring fish; they
then take flight and go to other waters, or are blown across the sea; and
we have seen that seeds retain their power of germination, when rejected
many hours afterwards in pellets or in the excrement. When I saw the great
size of the seeds of that fine water-lily, the Nelumbium, and remembered
Alph. de Candolle's remarks on the distribution of this plant, I thought
that the means of its dispersal must remain inexplicable; but Audubon
states that he found the seeds of the great southern water-lily (probably
according to Dr. Hooker, the Nelumbium luteum) in a heron's stomach. Now
this bird must often have flown with its stomach thus well stocked to
distant ponds, and, then getting a hearty meal of fish, analogy makes me
believe that it would have rejected the seeds in the pellet in a fit state
for germination.
In considering these several means of distribution, it should be remembered
that when a pond or stream is first formed, for instance on a rising islet,
it will be unoccupied; and a single seed or egg will have a good chance of
succeeding.
Pages:
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643