ARACHNIDA. 



317 



times woven together by zig-zag lines, and thus exhibiting a 

 structure of exquisite and most elaborate composition. The fluid 

 silk, which, when it is drawn through the microscopic apertures 

 of the spinneret, affords the material whereof the web is con- 

 structed, is secreted in a set of glands represented in the sub- 

 joined engraving (Jig. 148). The secerning extremities of the 

 glandular tubes are composed of branched cseca (&), whence arise 

 long and tortuous Fi 148 



ducts (a, a, a), 

 that become dilat- 

 ed in their course 

 into reservoirs for 

 the secreted fluid, 

 and terminate by 

 several canals at 

 the base of the 

 external spinning 

 tubuli. Various 

 are the purposes 

 to which the dif- 

 ferent species of 



the Araneidse convert the delicate threads thus produced. Some 

 construct for themselves silken tubes or cells, in which to conceal 

 themselves from pursuit, and from this retreat they issue to hunt 

 for prey in the vicinity of their abode ; others strew their fila- 

 ments about at random, apparently to entangle passing insects ; 

 many make nets composed of regular meshes, and spread them out 

 in favourable situations to entrap their victims (Jig. 146) ; while 

 a few species, enveloping their eggs in bags of curious construction, 

 carry them about attached to their bodies, and defend them with 

 the utmost courage and pertinacity : even in water these webs are 

 turned to* many singular uses ; and ropes, nets, and even diving- 

 bells are at the disposal of aquatic species furnished with this 

 extraordinary spinning machinery. 



A few only of the most remarkable applications of this de- 

 licate material can be noticed in this place. The mason-spiders 

 (Mi/gale) excavate for themselves subterranean caverns, in which 

 these marauders lurk secure from detection, even by the most 

 watchful foe : nor could any robber's den, which ever existed in 

 the wild regions of romance, boast more sure concealment from 

 pursuit, or immunity from observation. The construction of these 



