WEST 
105 
to their extremities; the expanded parts are extremely attenuated, so much so as to 
require a high 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 have been attached and moistened, these folds could be put upon the stretch, 
thereby lengthening the tubes, and consequently having a tendency to produce a vacuum, 
they vrould form an excellent apparatus for attachment." 
There must be some mistake here; hair-like organs of this kind, with corrugations, 
are (I believe, as the result of numerous observations) only present on the tarsi of those 
beetles which possess them for sexual purposes. Misled by preconceived ideas, although 
the correct term was applied to the appearance presented, a hypothesis is started to ac- 
count for it, of which the least that can be said is that it is quite inconsistent with the 
structure of the parts concerned. 
Gosse (1859)* describes the " strong divergent hooks " of the Fly's foot as being them- 
selves well clothed with spines f ; the difference in outline of the flaps in different species 
of flies ; their being " thin, membranous, and transparent," so that " when a strong light is 
reflected through them" .... " their structure is seen very distinctly." The appearance 
of " lozenge-shaped areas " on " the inferior surface of the palm " is also mentioned, and a 
conjecture is started as to their real nature. " From the centre of each area proceeds a very 
slender, soft, and flexible pellucid filament, which reaches downwards to the surface on 
which the fly is walking and is there slightly hooked and enlarged into a minute fleshy 
bulb. Those from the areas near and at the palms arch more and more outwards, so that 
the space covered by the bulbs of the filaments is considerably greater than that of the 
palm itself. Now it is evident that the bulbous extremities of these filaments are the 
organs of adhesion. We notice how they drag and hold, as the fly draws its foot from its 
place ;" the marks left on the glass by these " filaments " when " the foot is suddenly 
removed " are supposed to show " that the adhesion is effected by means of a glutinous 
secretion poured out in minute quantities from these fleshy tips." The necessary vitiation 
of the results when an insect is confined in a " nearly air-tight glass cell " is observed 
upon with a view to caution against building too much upon them. As already stated, 
j3u.ixa.0u «~^~~ n 
f; 
however, the experiment is easily repeated with flies moving on plane glass su 
where errors from this cause cannot arise. 
The inquiry is extended to the "similar appendages" on the "joints of the foot" of 
some Beetles. Timarcha tenebricosa is adduced as the first example; unfortunately the 
specialization of structure of these holding appendages is not well marked on the tarsi of 
this insect, though the " velvety cushion of a rusty-brown colour," is present, and very 
dense. The outline of the joints composing the tarsus is then mentioned ; with the 
absence of cushioned soles from the last, which "carries two stout hooks." "The first 
three " are described as " flat or even hollowed beneath into soles, something like the hoof 
of a horse ;" an excellent comparison, which may be extended even to the structure itself. 
It is only necessary to imagine the parts cemented together by an elastic material to have 
* Evenings at the Microscope, pp . 1 3 1 - 1 4 3. 
t See also Inman, p. 8, who considered this appearance of being " imbricated or covered with scales " to be owing 
to the claw having " its formation originally by cells." 
3l2 
