158 JOURNAL OF CONCHOLOGY, VOL. 10, NO. 5, JANUARY, I902, 



tain a horizontal position when only the tip of the tail remains upon 

 the object ; moreover, it can swing and curve its body in all directions, 

 and even at this juncture can return to the object it has so nearly 

 abandoned. If the forward motion is continued, it happens at last 

 that the tail no longer remains in contact with the object, and if every- 

 thing is favourable the animal is suspended by a gradually lengthening 

 thread, which is left by the body at the tail. It sometimes happens 

 that a slug, in this manner, reaches a new support without a fall. This, 

 however, is a comparatively rare event. Sometimes the animal falls 

 without a thread; at other times it makes but a very short one, and 

 often, perhaps generally, the thread fails after attaining a length of a 

 few inches. These remarks apply not only to heavy slugs but to 

 small ones capable sometimes of producing threads of surprising 

 length. In the writer's experiments, the twigs were in a few instances 

 three to four feet from a new support, but in most cases the distance 

 was less than a foot ; yet of twenty-two AgrioUniax agresfis only six 

 reached a support without a fall — of the remaining sixteen, four fell 

 without a thread or with less than two inches, and twelve with an aver- 

 age of nine inches. Of ninety-four slugs of various kinds (generally 

 small) not more than thirteen accomplished the journey successfully. 

 Thus the slug's descent is of a very uncertain kind. The animal's 

 ability to make and continue a thread is so doubtful, indeed, that one 

 is always prepared to see the creature fall ; and it is obvious that the 

 spinning-faculty here obtaining is of extreme imperfection. It is inter- 

 esting to note, however, that Bouchard-Chantereaux (lo) saw young 

 Limax arhorion descending from one branch of a iree to another, and 

 that Warner (35) saw a slug descend without a fall from a rafter in an 

 orchid-house, a distance of seven feet, D.T. (33), moreover, appears 

 to have seen the successful accomplishment of yet longer descents. 



The individual differences observable depend partly on the disposi- 

 tion of the animal and partly on the nature of its surroundings with 

 regard to light or shade, moisture or dryness, etc. Some seem deter- 

 mined at all risk to leave the object on which they are placed ; they 

 crawl off quickly, in a reckless manner, and the thread if formed at all 

 generally fails immediately. The ability to continue the thread depends 

 largely on the nature and consistency of the slime at the time of the 

 descent, and also, no doubt, on the regularity and continuity of the 

 supply. Harte (23) remarks that slugs kept for a night under a glass 

 spin better than those freshly taken, the slime being too thin when 

 they are gorged with food ; and the writer has found that spinning- 

 powers are apt to be increased by two to three days' confinement, with 

 a little water, in nearly air-tight tins. Ai'ion chxumscriptus spun ex- 

 cellently after having been in a tin, without food, for a fortnight. Tye 

 (31) on the authority of Harte's remark, has supposed that the animals 



