156 



INWERTEBRATE ANIMALS. 



simply for lining their habitations. 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 passing through what are called the 

 " spinnerets." These are little conical or cylindrical organs, from 



Fig. 104.— A, The male of the common Honse-Sjiider (Tegenaria civUis) considerably 

 magniHed : c Front portion uf the body, consisting of the amalgamated head and 

 thorax ; p Maxillary palpi ; a Abdomen. B, Front portion of the head of the 

 same, showing the eight eyes (/) and the mandibles (71). C, Under side of the head 

 and trnnk, showing the true jaws (m), the lower lip (I), and the horny plate to 

 which the legs are attached. D, Diagram of one of the air-chambers or breathing- 

 organs. (Figs. A, B, and C are after Blackwall.) 



two to eight in number, placeil at the end of thfe abdomen, and per- 

 forated 1 ly a luimber of e.xti'emely minute tube,?, through which the 

 secretion of the gland has to pass before reaching the air. Many 

 Spiders, however, do not construct any web, unless it be for their 

 own habitations, l)ut simply hunt their prey for themselves. 



The Spiders are oviparous, and their young pass through no 

 metamorphosis, but they cast their skin or " moult " repeatedly 

 before they attain the size of the adult. 



