MEMORANDA. 313 



power, on the same principle as that on which the boy wets 

 his leather to attach it to a stone ; that the fluid is not of a 

 glutinous nature, as it evaporates very rapidly, and I liave not 

 been able to detect anything on the glass afterwards, when 

 the foot has been perfectly t lean : that each sucker is under 

 the influence of the will, and has either muscular fibres or 

 other elastic tissue, which answers the same purpose [vide 

 Professor A. Ecker's paper. Journal, Vol. ii., page 111). If 

 the secretion were glutinous, and tlie foot were to be attached 

 for some time (twenty or thirty minutes, as I have often seen 

 it) to the same spot, it would get so firmly fixed, that if forci- 

 bly raised by the leverage of the hooks, these exceedinglv 

 delicate structures would be destroyed. The Di/tisciis, when 

 under water, is able to hold himself so firmly on glass, as to 

 require the weight of many pounds to overcome the power 

 with which he is attached ; whereas when the glass is dry, 

 there is no difficulty. I have seen a Fly (under the microscope 

 feet upwards) make one foot the centre of motion, and move 

 the body so far round it, as to cause the leg to form a consi- 

 derable angle (15 to 25 degrees). I conceive that, to overcome 

 the adhesion, if produced by a glutinous secretion, which is 

 sufficient to fix the foot under these circumstances, it would 

 require such an amount of power by means of leverage, as 

 would readily tear through the delicate ends of the tubules. 

 At other times, I have seen the insect so far loosen its hold, as 

 to allow the flap (cushion) to drag along the glass, and refix it 

 firmly, without lifting it off the glass. The round portion of 

 the flap of the blow-fly is about the 1-lOOth of an inch in 

 diameter, which contains upwards of 6,000 suckers ; t'te trian- 

 gular part, extending for attachment up to the leg, will be about 

 a quarter more of that area: the flaps of one foot, then, will 

 have 15,000 or 16,000 points of attachment. Diagrams, Nos. 

 1 and 2, are further illustrations of the same principle. No. 

 1 — Hairs from the pad of the foot of a small Curculio beetle ; 

 they expand into the form of a trumpet, and where the expan- 

 sion commences they appear corrugated, and the corrugation 

 is continued to their extremities ; tlie expanded parts are ex- 

 tremely attenuated, so much so, as to require a liigh power 

 and oblique light to make them out. These insects (not 

 being aquatic) also secrete a fluid for the same purpose as the 

 Fly : and I can imagine that if, after the ends liave been at- 

 tached and moistened, these folds could be put up<m the stretch, 

 thereby lengthening the tubes, and consequently having a 

 tendency to produce a vacuum, they would form an excellent 

 apparatus for attachment. 



No. 2 is the pad of a variety of Cijmbex lutea, which has 



