THE HAUNTS OF LIFE iii 



fisherman should have the bad luck to capsize his basket, 

 he might get the contents back again after many days. 

 The Bacteria reduce the dead fish to debris which Infu- 

 sorians devour, and to simple substances which plants 

 reintroduce into the circle of life. What was part of 

 the dead fish becomes part of Infusorian and Diatom ; it 

 enters into a new incarnation in the Crustacean ; it be- 

 comes again part and parcel of a fish. For it is thus 

 that the world goes round, and we have a curious bio- 

 logical commentary on casting bread upon the waters. 



An extraordinary outburst of vegetative life is sometimes 

 seen in canals, extending for many miles, and making 

 the water like green soup. The phenomenon is due to 

 various kinds of green Algae, but often it is one kind that 

 predominates. When this is Oscillatoria, the sight is 

 especially remarkable, for this type of filamentous blue- 

 green Alga has the habit of slowly bending backwards and 

 forwards in the water — as if it were trying to break its 

 vegetative chains. 



Origin. — ^When we ask in regard to a freshwater basin, 

 where its tenants came from, we are led to three answers. 

 (1) It seems quite clear that a certain number have come 

 from the sea, either by active migration, as we see the 

 elvers doing to-day, or by passive transport as in the case 

 of the freshwater sponges. When we find one family of 

 sponges (SpongilUdse) in freshwater, and a large number 

 of famihes in the sea, we may safely conclude that the 

 freshwater forms had a marine ancestry. Hydra and haK 

 a dozen other Hydrozoa live in freshwater ; all the other 

 Ccelentera or stinging animals are marine ; we need have 

 no hesitation in regarding the freshwater forms as derived 

 from marine ancestors. 



