SPINNING MOLLUSCS. 315 



The speculations of Belanger, it will be observed, here appear 

 as statements of established facts, Johnston having been misled 

 by Kiener, whose restatement of Belanger's observations wants 

 some of the precision of the original notes. Statements in other 

 books (some adapted from Johnston) also exceed what is really 

 known ; and some are further objectionable from the fact that 

 they do not make it clear that suspension is likely to be an 

 occasional circumstance, not the usual condition under which 

 the animal lives. 



Alaba picta, a Litiopid found by A. Adams among Zostera in 

 shallow water in the seas of Japan, is stated by him to spin a 

 pellucid thread, with great rapidity, from a viscous secretion 

 " emitted from a gland near the end of the tail"; it also creeps 

 at the surface of the water, and, when fatigued, suspends itself, 

 apex downwards, by means of the thread which is attached to the 

 surface.* 



Valvatid^s. 



Valvata piscinalis (familiar in our ponds and canals) was 

 observed to use a thread by Laurent. He noticed that the 

 animals, in crawling at the surface of water, deposited there a 

 trail of mucus, and that, when made to fall, some of them 

 remained suspended to the floating trail by a thread ; similarly, 

 others were sustained in the water when forced to leave the 

 branches of the plants on which they lived. In the former case 

 some were seen to remount to the surface of the water by 

 ascending their thread, which was gathered up by the foot.f 

 Mr. A. E. Boycott has written of the same animal, immature 

 specimens of which, in captivity, were seen by him actively 

 engaged in thread-spinning : — " Their usual mode of procedure 

 was to crawl up the side of a glass vessel nearly to the surface of 

 the water ; they then gave one or two twisting motions, and 

 crawled out on the under surface of the water, leaving a thread 

 joining them to their point of departure. They then either sank 

 slowly, remained floating, or sank about half way, where they 

 stopped." The thread, the presence of which was easily demon- 



* A. Adams, 'Annals and Magazine of Natural History' (3), x. (1862), 

 pp. 293-5, 419. 



f Laurent, ' Extraits des Proces-Verbaux des Seances de la Societe Philo- 

 matique de Paris,' 1841, pp. 118-9. 



