Page:The Zoologist, 4th series, vol 4 (1900).djvu/327

Rh inaccurate; but Mr. Taylor, replying to an enquiry, states that it represents an observation made in his aquarium in 1889; and assures me that he has several times witnessed the formation, by Limnæids, of short downward threads.

Amphipeplea.—The use of a thread by Amphipeplea glutinosa has been observed, as already noted, by Mr. Warington. One individual was seen to gradually rise, from a piece of rock in the aquarium, to a distance of three to four inches; it then stayed its progress, and soon afterwards rose suddenly and rapidly to the surface, the retaining thread having evidently given way. Professor Tate has remarked that the water in which this animal is kept, if shallow and insufficient, "is soon rendered glutinous with their mucus-threads"; and Mr. F.W. Fierke, who kept specimens in a jar, mentions threads of mucus "connecting weed to weed, and sometimes even decorating the shells of other molluscs with which L. glutinosa had evidently come in contact"; he mentions, also, having observed the animal gently rise through the water.

Planorbis.—In the flattened Limnæids of this genus (coil-shells), we are again indebted, for the first observation, to Mr. Warington, who appears to have seen the habit in several species. Mr. Tye saw it—less frequently than in Limnæa—in Planorbis spirorbis, P. carinatus, P. complanatus, and P. contortus, but not in six other species kept under observation. In P. complanatus the habit has been noted, also, by Mr. Musson.

Segmentina.—Segmentina lineata was kept by Mr. Tye, but was not seen to spin. We have a statement by Professor Cockerell, however, that one of his brothers, who had been keeping specimens in a bell-jar, had seen one "spinning a downward thread" from the surface of the water to the bottom of the bell-jar.

Ancylus: aberrant Limnæids (fresh-water Limpets).—Mr. Clark, long ago. saw that Ancylus fluviatilis living on pebbles in