86 



THE YOUNG 



NATURALIST. 



the maxillary palps ; 3. — a labium or lower 

 lip. There are just two points in these 

 appendages in which the Araneida differ 

 from the other orders of the Annulosa 

 deserving of mention, viz., that they possess 

 at the extremity of each mandible a sharp 

 moveable hook containing a duct communi- 

 cating with a poison gland situated in the 

 preceding joint of the mandible, and that in 

 the female the maxillary palps are termina- 

 ted in sharp claws which become occasion- 

 ally swollen. Dr. Nicholson thus remarks 

 on the nomenclature of these appendages : — 

 •'The nomenclature ordinarily applied to 

 the parts of the mouth in the Arachnida is 

 a misleading one, so far as the homologies 

 of this class with the Insecta are concerned. 

 Thus the so-called mandibles are really the 

 antennae. The mandibles themselves are 

 absent, but the chelae of the Scorpions (a 

 neighbouring order to the Araneida) may 

 really represent the mandibular palpi, 

 whilst the first pair of legs really corres- 

 ponds with the labial palpi, and the second 

 pair of legs may possibly be a modification 

 of the second pair of palps" (Manual of 

 Zoology, p. 300). This seems to be rather 

 confounding at first, but upon careful read- 

 ing we find the relationship to be homolo- 

 gous, not analogous, which renders it more 

 easy of comprehension. 



Digestion is carried on in a very simple 

 manner. The food, which mainly consists 

 of the juices of those animals on which they 

 feed, passes down the oesophagus or gullet 

 into the stomach, where it becomes digested 

 and distributed over the system. The waste 

 matter passes away by a short and uncon- 

 voluted intestine from the body. Numerous 

 salivary glands are present, and at the 

 terminal portion of the intestine ( cloaca ) 

 numerous tubes having a renal function 

 and seemingly analogous to the malpighian 

 vessels of the Insecta open. 



At this point perhaps it would be best to 

 make a mention of the arachnidum of the 



spider. This organ is situated at the 

 extremity of the abdomen, and secretes a 

 viscid fluid. This fluid is conducted down 

 from the arachnidum into four or six teat- 

 like glands called spinnerets (arachnidial 

 mammillae), each of which contains a large 

 number of minute tubes. Through these 

 tubes the viscid fluid is drawn, which 

 hardens rapidly on exposure to the atmos- 

 phere, and constitutes those beautiful geo- 

 metrical nets or webs so common on hedges, 

 old fences and palings. From the manner 

 in which these webs are constructed a 

 classification of spiders has been made, as 

 follows : — 



I. —OrHtelaria. — Those which spin a cir- 

 cular web with lines radiating from the 

 centre. 



II. — Retitelarice. — Those which spin a 

 thin suspended sheet. 



III. — TuhiteloA'ia — Those which construct 

 a silken tube in any accidental cavity, 

 the opening of which is guarded by 

 more or fewer threads. 



IV. — Territelarice.— Those which spin a 

 silken tube in a hole constructed by the 

 animals themselves, and close its mouth 

 by means of a variously-constructed 

 lid, 



" Still at the centre she her warp begins, 

 Then round at length her little thread she spins, 

 And equal distance to her compass leaves ; 

 Then neat and nimbly her new web she weaves, 

 With her fine shuttle circularly drawn 

 Through all the circuit of her open lawn — 

 Open ! lest else the ungentle wind should tear 

 Her cypress tent, weaker than any hair; 

 And that the foohsh fly might easier get 

 Within the meshes of her curious net, 

 Which he no sooner doth begin to shake. 

 But stiaight the male doth to the centre make. 

 That he may conquer more securely there 

 The humming creature hampered in his snare." — 

 Joshua Sylvestee. 

 Circulation is carried on as in the Insecta 

 and Myriapoda, by a vessel running along 

 the back, above the alimentary canal, called 

 the dorsal vessel. This is one of the simplest 

 forms of circulatory apparatus, consisting, 



