KEW : ON THE MUCUS-THREADS OF LAND-SLUGS. lOf 



the descent of Agr. agrestis and Arion liortensis; and was satisfied 

 that the habit was common to all slugs: 



Mr. riarte says that if a slug be gorged with food, the slime is . . . not 

 able to sustain it ; but if kept over-night without food, it performs well next morning. 

 This is a very interesting fact as showing that when the creature is in a condition 

 when it would be likely to require the thread most, viz., hungry and in search of 

 food, it is in a condition best suited t® produce it ; and this further strengthens my 

 belief (contrary to Mr. Harte), that the thread is used as a means of voluntary 

 descent. . . . When in search of new feeding grounds, during its excursions, 

 it would often come to the edge of an object and launch itself into space upon the 

 chance of finding a landing again soon, or if it did not, returning to its old one. 



32. Martens, E. von. Zur Kenntniss der fadenspinnenden 

 Schnecken, Zool. Anz., vol. i, 1878, pp. 249-51. 



The thread is drawn together, the author says, from the whole 

 slime-covering of the animal, whose body it embraces like the net- 

 work of a balloon; but this is a mistake. References are given to 

 Lister (i), Hoy (2), Shaw (3), Latham (4), Cuvier (5), Ferussac (7), 

 Clarke (13), Macgillivray (17), Forbes & Hanley (21), Harte (23), etc. 



33. D. T. Slugs spinning threads, T/te Field, vol. 54, 1879, p. 145. 

 A curious habit of the common slug [probably Agr. agresiis] has come under my 



notice. . . . Owing to the wet season, the clover placed in the loft over my 

 horses contains hundreds of them, and of course they very soon seek an escape to 

 /erra firma. Dozens of them may be seen letting themselves down by their slime, 

 slowly gyrating their bodies so as to spin it into a thread. Their rate of descent is 

 about an inch a minute. The height they descend is about nine feet, and they are 

 capable of spinning a thread of slime sufficiently long to reach the ground. 



34. Warner, R. Slugs in Orchid-Houses, Gard. Chron., n.s., vol. 



T4, 1880, p. 405: 

 When no other way is open to them, they crawl up some plant or rafter, and 

 . . . let themselves down to the spikes. I have known a small one let itself 

 down eighteen inches, and doubtless it could have gone much further. 



35. Warner, R. Slugs in Odontoglossum-Houses, Op. cit., vol. 16, 



1881, p. 722 : 

 . . . I caught a slug this morning letting itself down from the rafter. . . 

 When it had got to the ground, seven feet from rafter, I killed it — a small black one, 

 about one inch long. 



36. W[ard], J., in Roberts' Topography and Natural History of 



Lofthouse, 1882, p. 332: 



I had occasion to lift a plank which had lain some time among grass 

 and on the under-side I noticed a small slug, Liniax agrestis. On being turned to 

 the light the animal crept a few inches to the edge of the plank, and . . . began 

 to form a slimy thread, by the aid of which it let itself slowly and safely down to the 

 ground, a distance of three feet. 



37* Roebuck, W. D. Slime spinning by Arion hortensis, Jonrn. 

 Conch., vol. 4, 1883, p. 82. 



Arion hortensis v. rufescens [=A. siibfuscus~\ : 



Being placed on a flat paper-knife it walked straight off it, seemingly into the 

 air, and even while the end of its tail was the only part in contact with the paper- 



