382 ARACHNIDA. 



of smaller cords, sometimes woven together by zigzag 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 constructed, is 

 secreted in a set of glands represented in the subjoined engraving 



Fig. 194. 



Silk-secreting glands of the Spider. 



(fig. 194). The secerning extremities of the glandular tubes are com- 

 posed of branched cceca (s), whence arise long and tortuous ducts (a a a), 

 that become dilated 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 different species of the 

 Araneidae convert the delicate threads thus produced. Some construct 

 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 filaments 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 (fig. 192) ; 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. 

 (979.) A few only of the most remarkable applications of this deli- 

 cate material can be noticed in this place. The Mason-spiders (Mygale) 

 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 observa- 

 tion. The construction of these singular abodes has long excited the 

 admiration of the naturalist : a deep pit is first dug by the Spider, often 

 to the depth of 1 or 2 feet, which, being carefully lined throughout with 



