462 



NATURE S TEACHINGS. 



The creature is perpetually elongating and contracting its 

 body by means of these tubes, so that a measurement of its 

 length is not easy to obtain. 



A full and interesting description of this curious Eotif er may 

 be found in Gosse's " Evenings at the Microscope/' p. 300. 

 The long tails of the Rat-tailed Maggot, already described 

 under the head of Diving, are good examples of the draw- 

 tube as found in Nature. 



Locomotion. — Direct Action. 



The second point which has to be elucidated is that of 

 progress by means of Direct Action. 



NAUTILUS. 



LAEVA OF DRAGON-FLY. 



EOCKET. 

 "WATER TOURNIQUET. ELECTRIC TOURNIQUET. 



We have already seen how vessels can be propelled by sail, 

 oar, paddle, or screw. We have now to consider a mode of 

 progress which requires none of these things, but which works 

 by means of Direct Action. 



Such, for example, is the progress of a Rocket through the air. 



The heated gases rush out with tremendous violence, and, 

 by their pressure, urge the heavy rocket into the air with the 

 rush, roar, and bang so familiar to all who have witnessed a 

 good display of fireworks. 



