225 



Each consist of a cylindrical and slightly -conical tube, which 

 is filled with muscular tissue. The fibres terminate in a central 

 tendon : to this is attached a large membranous disc, by many 

 radiating lines. As soon as this disc is placed on any substance 

 the central tendon is drawn inwards, and the suction power is 

 complete. Fig. 32. The same muscles will draw these organs 

 within the sheaths whenever they are not in operation. 



These undoubtedly act as suckers. 



It is to be remarked that they have nothing to do with the 

 locomotion of the creature, and are entirely distinct from the 

 feet, which resemble those of the beetles. 



Experiment has shown that these are inadequate to the sup- 

 port of the creatures in air. Observation seems to have con- 

 firmed the usually received opinion that they are intended 

 merely to enable the insect to hold inseparable connection 

 with its mate during the spring time. 



I now propose to examine the question how far any of the 

 feet we have named can act as suckers. 



It will be evident I think, at once, that the very formation 

 of the feet disproves it. No one would ever be able to make a 

 vacuum in the receiver of an air pump, if the glass itself, or the 

 plate on which it was placed, were bristling with hairs like a 

 clothes brush. It would be equally impossible to fix a hat 

 brush, by atmospheric pressure, to our hats. 



Yet the bosses, if possible, are more densely covered with 

 hairs than either of these two. 



But as the force of prejudice is very strong, and persons may 

 doubt the strength of a simple proof like this, it will be advis- 

 able to add a few observations and experiments upon this parti- 

 cular point. I will commence with the most simple, and finish 

 with the most conclusive. 



Though I now speak from my own experience, I should be 

 unfair if I did not state, that the experiments are merely repe- 

 titions of those made by Mr, Blackwall six yeais ago, and 



2 o 



