218 MEANS BY WHICH ANIMALS ADHERE 
According to the observations of Sir Everard Home, 
they are expanded membranes, having their inferior 
surface granulated and their edges beautifully ser- 
rated *; while Messrs. Kirby and Spence, on the 
contrary, remark that they are downy on the under- 
side and granulated above ft. 
The want of accordance so conspicuous in the 
preceding accounts induced me to inspect the parts 
minutely under a good compound microscope, when 
it was immediately perceived that the function 
ascribed to them by Dr. Derham and Sir E. Home 
is quite incompatible with their organization. Minute 
hair-like papillz, very closely set and directed down- 
wards, completely cover the inferior surface of the ex- 
panded membranes, improperly denominated suckers, 
connected with the terminal joint of the tarsi of flies, 
the edges of which are plain, not serrated, as Sir E. 
Home asserts, though, when placed in such a situation 
relative to the eye of the observer that the hair-like 
papillae in connexion with them are foreshortened, 
they certainly present an appearance which, on a 
superficial view, might lead to the latter conclusion. 
This circumstance of the underside of the tarsal 
membranes of flies being densely covered with erect 
papille effectually prevents its bemg brought into 
contact with the objects on which those insects move 
by any muscular force they are capable of exerting: 
* «Transactions of the Royal Society’ for 1816, p. 323. 
+ ‘Introduction to Entomology,’ vol. ii. letter xxiii. 
