PYGMY WORKERS AND BUILDERS. 



Ill 



a perfect cocoon. At the end of about seventy-two hours 

 the work is clone. 



5. Having once commenced, the worm continues to 

 spin, and the thread is unbroken from one end to the 

 other. The cocoon is thus seen to be really a ball wound 



Tlie Silk-worm. 



from the inside. The thread which forms it is eleven 

 miles long, and weighs about six grains. Let us for a mo- 

 ment consider the prodigious activity of the silk-worm 

 while spinning its thread. To dispose of the silk, it moves 

 its head in all directions, each movement being about one 



