INTRODUCTORY. 5 



• 



not to impede its onward progress : but when a portion 

 of its body is once extended, and has penetrated into 

 the soil, they keep it firmly fixed, whilst the remain- 

 ing part is drawn after it by muscular contraction. 



Now, is not this a simple but interesting feature in 

 the anatomy of the worm, that should be known to 

 every one ? — ^yet how few, even of the best educated, 

 are aware of its existence ! How many anglers, do 

 you think, are there, who handle their poor victim as 

 frequently as we do our pen, and are yet unacquainted 

 with this fact ! 



And as regards the Fly : you need not even quit 

 your study or parlour to have an opportunity of wit- 

 nessing a strange, and, to the masses, inexplicable 

 phenomenon connected with the insect, namely the 

 mode iu which it walks upon the ceiling with its feet 

 upwards, or progresses upon the smooth vertical pane 

 of glass in your parlour window, setting at defiance a 

 well-known law of gravitation. If you are not able 

 to solve this mystery, ask some friend who possesses 

 a microscope to show you the foot of a fly under the 

 instrument, and you will find, that at its extremity it 

 is furnished with a pair of membranous discs, on 

 which there are disposed countless minute suckers, 

 that operate upon the inverted ceiling, or smooth 

 glazed surface over which the fly is marching, in the 

 same manner as did the leather sucker with which, as 

 a schoolboy, you were wont to amuse yourself in 

 lifting heavy stones : this is the simple, but eflFective 

 apparatus which enables the little creature to main- ■ 



