168 Eatracts from the Minute-Book of the Linnean Society. 
of the abdomen had been occasioned by the exhaustion 
of the aériform fluids it contained. To detach them 
from those stations, the employment of a small degree 
of force was found requisite. 
In prosecuting this subject, clean ** phials of trans- 
parent glass, containing spiders and various insects in 
the larva and imago states, capable of walking on their 
upright sides, were breathed into till the aqueous va- 
pour expelled from the lungs was copiously condensed. 
on their inner surface. The result was remarkable. 
The moisture totally prevented those animals from ob- 
taining any effectual hold on the glass; and the event . 
was equally decisive if a small quantity of oil was sub- 
stituted for the aqueous vapour. A similar consequence 
ensued also, when the flour of wheat, or finely pul- 
verised chalk, or gypsum, was thinly strewn on the 
interior surface of the phials, the minute particles of 
those substances adhering to the tarsal brushes of the 
spiders, the pulvilli of the perfect insects, and the 
under side of the feet of the larve. These facts, far 
from corroborating the mechanical theory, appeared 
quite inexplicable, except on the supposition that an 
adhesive secretion is emitted by the instruments em- 
ployed in climbing. The next point to be determined, 
therefore, was whether spiders, and insects in the larva 
and imago states, when moving in a vertical direction 
on clean glass, leave any visible track behind them. 
Careful and repeated examinations, made with lenses 
of moderately high magnifying powers, in a strong 
light, and at a favourable angle, speedily convinced 
me that my conjecture was well founded, as I never 
failed to discover unequivocal evidence of its truth; 
though 
