088 



SPINNING-APPAEATUS OF SPIDERS. 



single thread. It is doubtful, however, whether all the Spinnerets 

 are in action at once, or whether those of different pairs may not 



have dissimilar 

 Fig. 353. functions ; for 



whilst the ra- 

 diating threads 

 of a Spider's 

 Web are simple 

 (Fig. 354, a), 

 those which lie 

 across these, 

 forming its con- 

 centric circles, 

 or rather poly- 

 gons, are studded 

 at intervals with 

 viscid globules 

 (b), which ap- 

 pear to give to 

 these threads 

 their peculiarly 

 adhesive cha- 

 racter ; and it does not seem by any means unlikely that each kind 

 of Thread should be produced by its own pair of Spinnerets. It has 



Fig. 354. 



Foot, with comb-like claws of the common Spider 

 (Epeira). 



Ordinary thread (a), and viscid thread (b), of the 

 common Spider. 



been observed by Mr. R. Beck, that these viscid threads are of uni- 

 form thickness when first spun ; but that undulations soon appear in 

 them, and that the viscid matter then accumulates in globules at re- 

 gular intervals. — The total number of Spinning-tubes varies greatly, 

 according to the Species of the Spider, and the Sex and Age of the in- 

 dividual ; being more than 1000 in some cases, and less than 100 in 

 others. The size and complexity of the Secreting Glandulne vary in 

 like manner : thus in the Spiders which are most remarkable for the 

 large dimensions and regular construction of their "Webs, they 

 occupy a large portion of the Abdominal cavity, and are composed 

 of slender branching Tubes, whose length is increased by numerous 

 Convolutions ; whilst in those which have only occasional use for 

 their threads, the Secreting organs are either short and simple 

 Follicles, or are undivided Tubes of moderate length. 



