466 THE MICROSCOPE. 



the economy of such an animal is deserving of the micro- 

 scopist's attention. 



The several small appendages peculiar to the Spider tribe 

 are represented in fig. 231. Of these, the two longest at 

 No. 1, having articulated processes, appear to be feelers; 

 the others, being the organs by which their silky threads are 

 emitted, are four in number. Their structure is very re- 

 markable ; the surface of each of the spinnarets is pierced 

 by an infinite number of minute hole?, seen in No. 2, 

 from each of which there escape as many little drops of a 

 liquid, which, drying the moment they come in contact 

 with the air, form so many delicate threads. Immediately 

 after the filaments have passed out of the pores, they unite 

 first together, and then with those of the next, to form one 

 common thread ; so that the thread of the Spider is com- 

 posed of a large number of minute filaments, perhaps many 

 thousands, of such extreme tenuity, that the eye cannot 

 detect them until they are twisted together into the work- 

 ing thread. In the two pairs of spinnarets a different ana- 

 tomical structure is to be detected ; the pair above, which 

 are a little longer than the lower, show a multitude of 

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

 which therefore resemble a sieve. The other shorter pair 

 have projecting tubes independent of the perforations 

 which also exist (No. 3). The tubes are hollow, and per- 

 forated 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 envelope 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 



