TO POLISHED VERTICAL SURFACES, 225 
ency as a cleaning-apparatus and an organ of adhe- 
sion. and progression depends, principally, upon the 
mucus they emit, which is secreted in great abund- 
ance, and not upon the power of producing a vacuum. 
When this instrument is applied to the body of the 
insect, any extraneous matter immediately becomes 
attached to it, and the impurities thus collected are 
ultimately expelled by a fresh discharge of mucus and 
a peculiar motion of the papille. Larve of the 
Glowworm, kept in captivity for the purpose of ex- 
periment and observation, may be fed on earthworms. 
I may remark that snails, it is well known, can 
adhere to polished bodies by means of a mucous se- 
cretion; and from minutely inspecting preserved 
specimens of tree-frogs ({yle), and the lizards deno- 
minated Geckos, I am decidedly of opinion that those 
reptiles are enabled to run upon the vertical sides of 
smooth objects by the agency of adhesive matter 
emitted from pores and papille situated on the inferior 
surface of their toes. 
