326 MANUAL OF ZOOLOGY. 



are almost always leg-like, and are often of the same form in 

 the males. The latter, however, commonly have the ends of 

 the palpi tumid, in which case they appear to be employed for 

 the purpose of conveying the seminal fluid to the female, thus 

 exercising a reproductive function. 



Spiders (figs. 162, 168) are all predaceous animals, and many 



168. Araneida. Theridion riparinm (female). 



of them possess the power of constructing webs for the capture 

 of their prey or for lining their abodes. For the production of 

 the web, Spiders are furnished with special glands, situated at 

 the extremity of the abdomen. The secretion of these glands 

 is a viscid fluid, which hardens rapidly on exposure to air, and 

 which is cast into its proper, thread-like shape, by being passed 

 through what are called the "spinnerets." These are little 

 conical or cylindrical organs, four or six in number, situated 

 below the extremity of the abdomen, and possibly to be re- 

 garded as modified limbs. The excretory ducts of the glands 

 open into the spinnerets, each of which has its apex perforated 

 by a great number of minute tubes, through which the secre- 

 tion of the glands has to pass before reaching the air. Many 

 spiders, however, do not construct any web, unless it be for 

 their own habitations, but hunt their prey for themselves. 



The form of the web has been employed as a basis of classification of the 

 Spiders, and amongst its numerous modifications, the following may be 

 specially alluded to : Some forms (such as the common Garden-spiders) 

 construct a web in the form of an incomplete or complete circle, with lines 

 radiating from the centre. These have been termed " Orbitelarice" Others 

 the so-called " Retitelaria " simply spin a thin suspended sheet for their 

 web. Others (" Tu&itdaria") construct a silken tube, inserted in any acci- 

 dental cavity, its mouth being open and guarded by more or fewer threads. 

 Lastly, others (" Territelarice") spin a silken tube in a hole formed by the 

 animal itself, and close its mouth by means of a variously-constructed lid. 



The Spiders are oviparous, and the young pass through no 



