896 MR. TUFFEN "WEST ON THE FOOT OF THE FLY. 



A figure which is given of the part is then clescrihed at length, but it is not necessary 

 to repeat the details here. The figure purports to be a representation of " almost a fourth 

 part of one of the legs, consisting of four distinct joints : there " are two claws or nails, 

 which are in some sort transparent, like a piece of horn or tortoise-shell seen with the 

 naked eye," and "organs" (on the ' deeply-bilobed third tarsal joint'*) "by the help of 

 which the animal can run along the smooth surface of the glass, and also hang to it a 

 whole night. The formation of these organs is very wonderful, for all those parts 

 witli which they are covered, and which one would conclude to be hairs, are so 

 exactly and regularly sloped oif, and particularly of such regular lengths, as if they had 

 been clipped with scissars, that when the animal places its foot anywhere, they all touch 

 the place at the same time, and what is more, all these particles, which seem to the eye 

 to be hairs, have at their extremities a hook, and at a little distance from thence, two 

 other hooks ; but by reason of their extreme minuteness, though the limner confessed he 

 saw them through the microscope, he declared he could not represent them through the 

 drawing. Now if we consider, what I have always experienced, that a glass, though 

 washed ever so clean, will have many particles adhering to it, though these are so small, 

 that the claws on the feet of flying insects cannot take hold of them, we may easily con- 

 ceive that these small hooks may take hold of the small particles of water or motes from 

 the air adhering to the glass. And here we may discover the error of those, who for- 

 merly supposed there were cavities in glass, v\^lierein flies could fix their claws, and climb 

 upt." 



I form no opinion of the absolute correctness of Leeuwenhoek's description of the 

 parts which "seem to the eye to be hairs," with "at their extremities a hook, and at a 

 little distance from thence, two other hooks," which, "by reason of their extreme 

 minuteness, though the limner confessed he saw them through the microscope, he declared 

 he could not represent them through the drawing," until I have been so fortunate as to 

 obtain living specimens for examination. I have scarcely, as yet, detected one error of 

 observation in the descriptions by the present author, of his extended microscopical 

 researches into objects embraced by the three grand kingdoms of Nature, and am therefore 

 unwilling to ascribe error to this portion of the present observation, without feeling per- 

 fectly clear that such error exists. An instatLce of an analogous structure will be men- 

 tioned presently, which perhaps may help to explain the meaning of the appearance 

 which he thus describes. 



By his careful, and at the same time lively, description of the remarkable liolding and 

 climbing organ of the " Sea-Mussel" (byssus of Modiola vulgaris) he shows that he was 

 fully acquainted with one instance at least of organs acting really by suction : his 

 observations on this head will be mentioned further on, in the course of my own remarks 

 upon such organs when presented by insects. 



Derham's claim (1798) t to rank as an original observer rests, so far as I can ascertain, 

 on very slender grounds. Yet, to judge from the influence which his remarks have had 

 in the forming of the opinions of men of the highest scientific acumen, even at the present 



* Westwood, «;«;»». t 0^3. C!it. part 3. pp. 186, 187. % Physico-theology, Part ii. p. 289. 



