134 ARACHNIDA. 



however, appear to have neither pores nor papillae. On ex- 

 amining the spinnerets more minutely, it will be found that 

 each is surrounded with several scries of minute bristles, like 

 points, about one thousand to each spinneret. From each 

 of these points or spinnerules is discharged a thread, so that 

 it may be easily conceived of what an immense number of 

 distinct threads the apparently simple thread of the spider 

 consists. The first object which the spider has to accom- 

 plish is to attach her thread to some substance, as the com- 

 mencement of a ground-work for her future operations. In 

 doing this, it appears that she extends her spinnerets as 

 widely as possible, presses them against the object to which 

 it is intended the thread should be attached, and then dis- 

 charges a thread from each of the spinuerules; the spinnerets 

 are then withdrawn, and the threads, by degrees, are united 

 into a single cord ; the insect uses her hind legs as a reel to 

 draw the threads out of her body. It appears, however, that 

 the threads are of different kinds ; for in the webs of the 

 geometric spiders, those threads which are arranged in circles 

 are composed of more viscid materials than the radii, the 

 former being evidently intended for securing the prey of t la- 

 spider, and the latter serving merely as its frame-work, and 

 destitute of gluten. This viscidity is produced by an im- 

 mense number of globules of viscid matter, arranged at 

 visible distances along the elastic spiral lines of the net, and 

 which are so fluid that they run together the moment they 

 are brought into contact. Mr. Blackwall has given a calcu- 

 lation of the number of these viscid globules in the web of 

 one of the Epeiree of a moderate size, and which comeys 

 some idea of the elaborate operations of the geometric 

 spiders. The mean distance between the radii in one of 

 these nets is about semi-tenths of an inch; there are twenty 

 viscid globules on one-tenth of an inch, so that there are 

 7 X '20 sss 140 globules in a single line between two contigu- 

 ous radii seven-tenths of an inch apart : this product, midti- 



