Earthworms Drowned in Puddles

Abstract

I HAVE long been familiar with the frequent occurrence of dead earthworms in surface “puddles” alongside gravel walks or roads, as described by Mr. Friend in NATURE of April 7, p. 172. I have supposed that they were “drowned” owing to the amount of free oxygen in the stagnant puddles being insufficient for their respiration. So far as I recollect, earthworms are not drowned (or, at any rate, not quickly) if they get into cool, clear, running water—which, presumably, contains a larger amount of dissolved free oxygen than does the rain-water accumulated about dead leaves and deoxidising or “reducing” mud. (See on this matter Darwin's “Vegetable Mould and Earthworms”, pp. 13–16.) I confess that I do not know the facts as to the percentages of free oxygen and of oxygen-seizing matter in natural fresh-waters, or, indeed, in sea-water, in various circumstances; nor do I know the percentage of free oxygen necessary in water in order that it may—even for the brief period of an hour or two—support the life of an earthworm. I should be glad to know if these quantities have been determined. It is a common practice to kill earthworms for dissection by drowning them, but I think the water used is warmed. Many years ago I employed “normal saline solution” in the dissecting trough.