182 NATCKAL HISTOKY SOCIETY OF DUBLIN. 



flower buds just formed ; also, for comparison's sake, he showed plants 

 in full bloom of Orchis maculata and of 0. Morio. He likewise took 

 the opportunity to exhibit flowering specimens of a few other rare 

 British Orchids, viz. — Lister a cor data, from Lough Bray; Orchis militarise 

 and Herminium monorchis. The two latter have not been found in 

 Ireland. 



The Honorary Secretary, in the absence of the author, then read the 

 following paper : — 



jSTote on certain Movements of the Limacid^;. By William Haete, 

 C.E., F.R. G.S.I. 



Some time since my attention was caught by a slug descending from the 

 branch of a tree in my garden, and which had lowered itself by a thread 

 some three or four feet. The circumstance was then new to me; it is, 

 however, on record that these animals have the power of doing so, 

 though it does not seem to be common.* But on experimenting on them, 

 I observed one fact which I believe is new, viz., that they possess the 

 power of reascending by means of the same thread ; and I am inclined 

 to think that this accounts for the fact of their being so seldom seen de- 

 scending. The leaving the branch in the first instance I believe to be 

 altogether an involuntary act. A slug descends by creeping along a 

 drooping branch, when it comes to the extreme point of which it may 

 be seen projecting over the end, seeking for fresh footing, its body 

 meanwhile slipping down by gravitation ; and at last, having lost its hold, 

 it is supported only by means of a thread formed by the secretion which 

 takes place over the whole surface. This secretion is first a broad 

 patch, the breadth of the foot ; it narrows into a fine thread, and then 

 gets tough by exposure to the air. It continues to descend by gra- 

 vitation alone ; and if the condition of the animal, or the atmosphere, is 

 not favourable to a continued secretion, it stops after having lowered itself 

 a few inches. The body is then slightly curved upwards ; and after 

 seeking for a while for a landing place, it is coiled into a spiral form, 

 from the centre of which the head is elevated along the thread, and the 

 position of the animal becomes reversed ; the mantle closes considerably 

 upon the thread, and (the foot being twisted half round) the animal then 

 ascends with a tolerably even gyratory motion, the "slack" of the 

 thread sometimes accumulating below the tail. 



Having inserted a branch of a weeping ash tree with several forks 

 on it, into a flower pot, and by putting some of the slugs upon the 

 branches, I have never found any difficulty in getting them to descend, 

 sometimes as much as five to six feet. The slug which I have found 

 to possess this power is the small grey garden slug, particularly the 



* Hoy, in "Linnaean Transactions," Feb. 1790, vol. i., p. 183; and Latham, "Linn. 

 Trans.," 1798, vol. iv., p. 85; Clarke, "Annals of Nat. History," 0. S., vol. xii., 

 p. 334. 



