396 MR. TUFFEN W 
A figure which is given of the part is then described 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 eve," 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 off, 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, wherein flies could fix their claws, and clinm 
upf." 
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 o 
observation in the descriptions by the present author, of his extended microscopica 
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 instance 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 holding WW 
climbing organ of the " Sea-Mussel " (byssus of Modiola vulgaris) he shows that he 
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 reniarKS 
upon such organs when presented by insects. 
Derham's claim (1798) % to rank as an original observer rests, so far as I can ascertain 
on yery slender grounds. Yet, to judge from the influence which his remarks have ha^ 
in the forming of the opinions of men of the highest scientific acumen, even at the presen 
Westwood 
t 
+ Physico-theology, Part ii. P< 289 ' 
