CHAPTER XIII 
ARACHNIDA EMBOLOBRANCHIATA (CON TINUED)— ARANEAE— 
EXTERNAL STRUCTURE—INTERNAL STRUCTURE. 
Order III. Araneae. 
(ARANEIDA,! ARANEINA.) 
Arachnida breathing by tracheae and “ lung-books.”  Cephalo- 
thorax and pedicellate abdomen, the latter usually soft, and only 
very rarely showing any traces of segmentation. Two-jointed non- 
chelate chelicerae, the distal joint bearing the orifice of a porison- 
gland. The tarsal joint of the male pedipalp develops a sexual 
organ. The abdomen is furnished with spinning mammillae. 
THE true Spiders can readily be distinguished from allied Arachnid 
groups, with which they are often popularly confounded, by the 
presence of a narrow constriction or “waist” between the 
cephalothorax and abdomen, and of a group of “spinnerets ” or 
external spinning organs beneath the hind portion of the body, 
Thus the so-called “ Harvest-spider ” or “ Harvestman” is clearly 
not a Spider, for there is no constriction of its body into two 
parts, nor does it possess any spinnerets. It belongs to the 
Phalangidea. The same considerations will exclude the “ Red 
Spider ” of popular nomenclature, which must be referred to the 
Acarina or Mites. 
The Araneae, even as at present known, form a very extensive 
and widely-distributed order of animals. Compared with certain 
insect orders, they have received little attention from the collector, 
5) 
' The term mostly in use is Araneida, which should mean Araneus-like animals. 
This is clearly not allowable, unless there is a genus Araneus or Aranea. For 
many years there has been no such genus recognised, but Simon now attempts to 
re-establish it, inadmissibly, as it appears to us. (See note, p. 408). 
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