SPINNING MOLLUSCS. 297 



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 

 Limnseids, of short downward threads. 



Amphipeplea. — The use of a thread by Amphipeplea glutinosa* 

 has been observed, as already noted, by Mr. Warington. One in- 

 dividual 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 " ;f and Mr. F. W. Fierke, 

 who kept specimens in a jar, mentions threads of mucus " con- 

 necting 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 Limnseids 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 Limncea — in 

 Planorbis spirorbis, P. carinatus, P. complanatus, and P. contortus, 

 but not in six other species kept under observation. In P. com- 

 planatus 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. IF 



Ancylus : Hberrant Limnseids (fresh-water Limpets). — Mr. 

 Clark, long ago. saw that Ancylus fluviatilis living on pehbles in 



* Limncea glutinosa. 



| Tate, « Land and Fresh-water Mullusks of Great Britain,' 1866, p. 198. 

 I Fierke, ' Journal of Conchology,' vi. (1890), p. 253. 

 § Musson, 'Land and Fresh-water Shells of Nottinghamshire,' 1886, MS. 

 || Planorbis lineatus. 



IT Cockerell, "Segmentina lineata, Walker, a Thread-spinner," 'Zoolo- 

 gist' (3), ix. (1885), p. 267. 



