THE AEACHNIDA. 



301 



with great care, so that there are as many above as in 

 the cup. It then finishes spinning the cocoon. 



512. The Caterpillars spin from the head, but the Spi- 

 der spins from the other extremity of the body. Its spin- 

 ning apparatus is of peculiar construction. Inside is a 

 reservoir of gummy matter from which the silk is made. 

 The threads of a Spider's web are drawn out from it, 

 and dry as fast as they are drawn. But the thread, which 

 appears to the eye as single, is found by the microscope 

 to be composed of many thousands of threads united to- 

 gether. In Fig. 234 you see, as the Spider hangs by his 



thread, that it comes 

 out from a circular 

 spot. In this are four 

 and sometimes six 

 knobs, which can be 

 seen by the naked eye. 

 Each of these is full of 

 holes through which 

 the threads come, and 

 these holes are so mi- 

 nute that Reaumur cal- 

 culated that a thou- 

 sand occupied a space 

 no larger than the 

 point of a pin . In Fig. 

 235 (p. 302) is repre- 

 ^'s- 234 sented such a view of 



these knobs as you would get by a powerful microscope. 



A portion only of the minute threads are represented. 



It was the calculation of Leuwenhoeck that it would 



take four milhons of them to make a thread as large as a 



hair. 



513. These threads are united together about one tenth 

 of an inch in distance from the spinnerets. By this sep- 

 arate exposure to the air of each threadlet, they all be- 

 come dry before their union. Another advantage of this 



