184 THE ORIGIN OF SPECIES 



of dispersal explain this fact. I have before mentioned 

 that earth occasionally adheres in some quantity to the 

 feet and beaks of. birds. Wading birds, which frequent 

 the muddy edges of ponds, if suddenly flushed, would 

 be the most likely to have muddy feet. Birds of this 

 order wander more than those of any other; and they 

 are occasionally found on the most remote and barren 

 islands of the open ocean; they would not be likely to 

 alight on the surface of the sea, so that any dirt on their 

 feet would not be washed off; and when gaining the 

 land, they would be sure to fly to their natural fresh- 

 water haunts. I do not believe that botanists are aware 

 how charged the mud of ponds is with seeds; I have 

 tried several little experiments, but will here give only 

 the most striking case: I took in February three table- 

 spoonfuls of mud from three different points, beneath 

 water, on the edge of a little pond: this mud when dried 

 weighed only 6| ounces; I kept it covered up in my 

 study for six months, pulling up and counting each 

 plant as it grew; the plants were of many kinds, and 

 were altogether 537 in number; and yet the viscid mud 

 was all contained in a breakfast cup! Considering these 

 facts, I think it would be an inexplicable circumstance 

 if water-birds did not transport the seeds of fresh-water 

 plants to unstocked ponds and streams, situated at very 

 distant points. 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 



