ON AERONAUTIC SPIDERS. 269 
when the spiders were placed where the air was liable 
to be sensibly agitated: I resolved, therefore, to put 
bell-glasses over them ; and in this situation they re- 
mained seventeen days, evidently unable to produce a 
single line by which they could quit the twigs they 
occupied without encountering the water at their 
bases, though, on the removal of the bell-glasses, 
they regained their liberty with as much celerity as in 
the instances already recorded. 
The manner in which the lines of spiders are carried 
out from the spinners by a current of air appears to 
be this. As a preparatory measure, the spinning- 
mamumule are brought into close contact, and viscid 
matter is emitted from the papille; they are then 
separated by a lateral motion, which extends the 
viscid matter into fine filaments connecting the 
papilla ; on these filaments the current impinges, 
drawing them out from the spinners to a length which 
is regulated by the will of the animal; and on the 
mammule being again brought together the filaments 
coalesce and form one compound line. 
The foregoing experiment, which, from a want of 
due precaution in its management, has misled so many 
distinguished naturalists, I have repeated with more 
than thirty distinct species of spiders, at all hours of 
the natural day, and in electrical and meteorological 
states of the atmosphere differing most essentially ; 
in short, under every variety of circumstances which 
appeared likely to influence the result, yet always 
