active a state as when the creature was in motion. I would add, also, as adverse to the opinion of the French naturalist, that in the Eolis and other floating species I have distinctly observed the action of the foot muscles; the animal, indeed, literally crawls on the under surface of the stratum of air, just as if it were a plate of glass.
The curious habit which these Water-snails have of rising perpendicularly through the water, and the still more curious power of spinning a thread, by the help of which this feat is accomplished, have been already described in the earlier pages of this work. I shall merely add to these particulars of their history, that they lay in summer large oval masses of clear jelly, which they affix to the stalks and leaves of submerged plants. Each mass contains from 100 to 130 eggs, which are hatched in sixteen days.