153 

 ON THE MUCUS-THREADS OF LAND-SLUGS. 

 By H. WALLIS KEW. 



(Continued from p. 103). 



Part II. 



During 1887-1896 I made a number of notes on various slugs, and 

 was able to make a drawing of an Arion in the act of ascending its 

 thread (fig. 5). In most of the experiments the animals were placed 

 on twigs of needle-furze. 



Limax maximus. — Young individuals when placed on the twigs 

 soon let themselves down, but fell with {-9 inches of thread. I have 

 not been able to induce full-sized or even half-grown individuals to 

 spin. 



The only specimen of L. cinereo-niger I have seen was a heavy 

 adult which could not be induced to s[)ia ; and with L. flavus I have 

 been unsuccessful both with adults and young. Several young, exposed 

 to the full light of a window, and to sunshine for a time, always turned 

 back on reaching the tips of the twigs and did not drop during the 

 twenty minutes I had them under observation ; after twenty-four days' 

 captivity they were observed for more than an hour with similar results. 



L. arborum. — Numerous young fell without threads or with short 

 ones ; two reached new supports after spinning eight inches. 



Amalia SOwerbyi. — A full-grown specimen of this somewhat large 

 slug soon commenced a descent and did not fall until it had been sus- 

 pended about five minutes, during which, however, it had made only 

 six inches of thread; others dropped with very short threads. A number 

 of young (either of this or the next species), about i^ inches long and 

 slender when extended, descended readily, and during the operation 

 their bodies, instead of being held for the most part in the ordinary 

 crawling position, were much twisted, so that parts of the dorsal and 

 ventral surfaces were presented to view together ; the thread some- 

 times proceeded from some little distance from the tip of the tail (in 

 some cases a quarter-of-an-inch) ; and the slime in these cases was seen 

 leaving the whole width of the sole in the form of a' contracting film. 



A. gagates, — One, about an inch long, fell with hardly more than 

 half-an-inch of thread. 



Agriolimax agrestis, — A full-grown field-slug dropped with ten 

 inches of thread, the production of which occupied about two minutes; 

 the thread vanished into a speck of whitish slime when the slug fell. 

 Among other full-grown individuals, one made twenty inches of thread 

 before dropping, and another thirty inches. One was lifted by its 

 thread and carried a little distance. A nearly full-grown specimen 

 descended eighteen inches, then turned and ascended about an inch, 



