284 



THE MICROSCOPE. 



small perforations, the edges of which do not project, and which there- 

 fore resemble a sieve. The other shorter pair have projecting tubes 

 independent of the perforations which also exist (No. 3). 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 may 

 be observed, 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 circumference ; the latter are also 

 stronger than the others. The rapidity with which these webs are 

 constructed is astonishing, as is also 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 gauge to measure her work, 

 in the same way as a bird uses its body to gauge 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 round its body during the 



1. Spinnarets of the spider. 2. Extreme end of one of the upper pair of spinnarets. 

 3. End of under pair of spinnarets. 4. Foot of the spider. 5. Side view of eye of 

 spider. 6. The arrangement of the eight eyes. 



process. It then, in the same manner, spins a raised border round this 

 till it takes the form of a cup, and at this stage of the work it begins 

 to lay its eggs in the cup, not only filling it with these up to the brim, 

 but piling them up above it into a rounded heap, as high as the cup is 



