G±6 



THE MICROSCOPE. 



in those above. The tubes are hollow, and perforated at 

 their extremities ; and it is supposed that the agglutinating 

 threads issue from these tubes, while those emitted from 

 the perforations do not possess that property. It will be 

 seen, by throwing a little dust on a circular Spider's web, 

 that it adheres to the threads which are spirally disposed, 

 but not to those that radiate from the centre to the cir 

 cumference ; the latter are also the stronger of the set. 



Fig. 299. 



], Spinnnrets of Spider. 2, Extreme end of one of the upper pair of spinna- 

 rets. 3, End of under pair of spinnarets. 4, Foot of Spider. 5, Side view 

 of eye. 6, The arrangement of the four pairs of eyes. 



The rapidity with which these webs are constructed is 

 as astonishing as is the accuracy with which the webs 

 are formed. There are many different kinds of Spiders ; 

 but nearly all of them envelop their eggs in a covering of 

 silk, forming a round ball, which the Spider takes care to 

 hang up in some sheltered place till the spring. The 

 mode in which the ball is formed is very curious : the 

 mother Spider uses her own body as a guage to measure 

 her work, in the same way as a bird uses its body to 

 guage the size and form of its nest. The Spider first 

 spreads a thin coating of silk as a foundation, taking care 

 to have this circular by turning its body round during the 

 process. In the same manner it spins a raised border 



