296 THE ZOOLOGIST. 



launched itself off from it; and, after moving about with a sort 

 of swimming or rolling motion in a horizontal direction for some 

 time, lowered itself gradually. During the descent, the flexible 

 leaf was bent with an undulating motion, corresponding with 

 every movement of the Snail, and making it clear that the 

 animal had an attachment to the extremity of the leaf. Proof 

 of the existence of a thread was obtained also by means of an 

 experiment which the observer often repeated with Limnaa 

 stagnalis, L. auricularia, and Amphipeplea glutinosa* When 

 the Snails were some inches from the supposed point of attach- 

 ment, a rod was introduced, and slowly drawn on one side in a 

 horizontal direction ; and, by this means, the Snails were made 

 to undulate to and fro, obeying exactly the movement of the rod. 

 This had to be done gently, for when too much force was used 

 the thread broke, and the animal rose rapidly to the surface. 

 According to Mr. Tye's observations, Limncea glabra spins its 

 upward thread well and easily ; L. stagnalis, when young, does 

 the same, but the habit decreases as the animal grows older ; 

 the same is the case with L. palustris, which, however, was 

 not seen to use a thread as often as L. stagnalis. L. auricularia, 

 L. truncatula, and L. peregra, though kept under observation by 

 Mr. Tye, were not seen by him to spin. Mr. R. M. Lloyd, how- 

 ever, had observed the habit in the last-named species. The 

 present writer has noted L. peregra and L. palustris, presumably 

 retained by threads, slowly rise through the water in aquaria ; 

 the L. peregra, which was extended as if crawling on a solid 

 body, did not always keep its foot in the same plane, from which 

 fact the writer concludes that it was not creeping up a thread 

 already fixed. The water through which it rose was about eight 

 inches deep ; and, on arriving at its destination, the animal 

 applied its foot to the surface-film of the water, under which it 

 crept in the usual inverted position. In L. auricularia, the use of 

 a thread was observed, as we have just seen, by Mr. Warington. 

 Mr. Taylor, also, has seen this species spin, and has recently 

 published a figure of an individual using a thread. This figure 

 (Fig. 1) shows the animal, moderately extended from its shell, 

 suspended from the surface of the water upon a downward-spun 

 thread. The drawing was at first supposed by the writer to be 

 * Limncea glutinosa. 



