Aberrations of Instinct 



this end it pokes its head to the end of 

 the roughly-defined funnel and then with- 

 draws it, doubling the thread as it goes. 

 This alternation of thrusts and withdraw- 

 als results in a circle of doubled filaments, 

 which do not adhere to one another. The 

 shift is not a long one; when the palisade is 

 a row the richer, the caterpillar resumes its 

 work upon the shell, a task which it again 

 abandons to busy itself with the funnel; and 

 so on, over and over again, the emission of 

 the gummy product being suspended when 

 the threads are to be left free and copiously 

 effected when they have to be stuck together 

 in order to obtain a solid texture. 



The exit-funnel is not, as we see, a piece 

 of work executed continuously; the cater- 

 pillar works at it intermittently, as the gen- 

 eral shell progresses. From the beginning 

 to the end of its spinning-period, so long as 

 the reservoirs of silk are not exhausted, it 

 multiplies the tiers without neglecting the 

 rest of the cocoon. These tiers take the 

 form of cones enclosed one within the other 

 and of increasingly obtuse angles, until the 

 last to be spun are so flat as to become al- 

 most level surfaces. 



If nothing happen to disturb the worker, 

 the work is performed with a perfection 

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