PHYSIOLOGY OF THE INVERTEBRATA. 



269 



tiuuation of the thread. This power of spinning threads 

 from the secretion of these glands is of the greatest import- 

 ance to all these animals (^i.c, those belonging to the 

 sedentary class), as it not only serves many of them for the 



Fig. 51, A AND B. — Malpighian Tubes of Tegenakia. 



construction of dwellings, and of webs for the capture of 

 prey, but is constantly employed in securing them from falls 

 whilst in motion, or in descending in a direct line from an 

 elevated position to some object below them. Many sj^iders 



