KEW : ON THE .MUCUS-THREADS OK LAND-SLUGS. 93 



in the animal to produce ?. continual supply of this liquid, and to make it flow 

 towards its tail. For this end it alternately pushed out its head, and drew it back 

 again below its shield ; turning it as far as possible, first to one side and then to 

 the other, as if thereby to press its sides, and so to promote its secretion. This 

 motion of the head in a horizontal direction to one side, made its whole body turn 

 round ; whereby the line by which it hung was necessarily twisted, and from being 

 flat became round. Besides, it might perhaps tend to draw off the glutinous matter, 

 and thus lengthen the line; which could scarcely be effected merely liy the weight 

 of the slug. 



The animal is characterised as Umax (filans) cinereus margineflavo : 

 and has been variously referred to Agriolimax agresiis, Umax flavits, 

 and Z. arhorum; and Mr. Roebuck lias suggested to me that it may 

 have been Avion snbfuscus. It is certainly not a distinct kind of slug 

 distinguished by the faculty of making thread, the spinning-slug 

 {Umax fi I a lis) of authors being a myth — a name applied to any slug 

 observed to spin. Ferussac erroneously supposed Hoy's slug to be 

 necessarily identical with spinning-slugs of Latham {4) ; these belonged 

 to Agr. agresfis, and were referred by Latham to a variet}' of that 

 species — Umax albus clypeo flavescente Miiller. This variety, sub- 

 sequently named L. agrestis \w. filans by Moquin-Tandon, has been 

 raised to the rank of a species by Mabille as L. filans. 



3. Shaw, G. Tom. cit., p. 185. 

 Shaw adds a note made in 1776: 



Sitting in an arbour about eight feet high I was amused with a very uncommon 

 spectacle, which I at first took for a Caterpillar hanging by its thread, and reaching 

 to within a foot of the ground ; . . . on a nearer view I perceived it, to my 

 great surprise, to be a small Slug, about three-quarters of an inch in length. It 

 hung by the extremity of its tail, and gradually descended till it almost touched the 

 ground, when I shook it off with my finger. 



This observation and that of Hoy make it clear, Shaw says, that the 

 animals of the genus '■^ Umax" have a power of occasionally managing 

 their glutinous excretion in such a manner as to serve the purpose of 

 a thread in a direct descent. 



4. Latham, J. Observations on the Spinning Limax, Op. cit., 



vol. 4, 1798, p. 85-9. 



Latham records observations made by Montagu on Agrio/iniax 

 agresfis : 



On my friend's putting one of them on the projecting frame of a window, it imme- 

 diately crawled forwards till it came to the projecting angle, from whence, without 

 attempting to fix itself by its fore parts to any thing, it became visibly suspended Ijy 

 a thread from its tail. 'When it had descended about two feet, the Colonel took it 

 up by the thread, and carried it to a distant room; but in trying to fix it afresh 

 the thread broke. He then put it on a frame about four feet from the 

 ground ; in a few minutes it was again suspended, and observing by his watch. 

 descended at the rate of three inches and a half in a minute. . . . When the 

 Slug was near the ground, an attempt was made, by taking hold of the thread near 

 to the body, to fix it afresh, but the thread again broke, as it did likewise on being 

 tried three other times \\\ih the sanie view, each time the Slug having nearly reached 



