XIV PREFACE. 



enjoying life, and grouped together in this 

 curious manner for mutual support. Let us ex- 

 amine it, and you will then be able to believe the 

 evidence of your own senses. You see before 

 you a hollow globe, formed of a material suffi- 

 ciently transparent for you to see within it. 

 Now look at the green dots with which it is 

 spotted thickly, but evenly, all over; they are 

 living beings, attached to the inner side of the 

 globe, each having an eye and a double proboscis, 

 which it protrudes from an opening in the trans- 

 parent case, and by which it has communication 

 with the exterior, and obtains its food. See how 

 actively each moves this instrument, and what 



