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®ii the ipreaence of a ^areaUconib in Spiders 

 of tbe family S^beribif)^- 



By Frederick O. Pickard Cambridge, B.A, 



ALTHOUGH there are few naturalists who make a systematic 

 study of the Araneida or spiders, yet there are many 

 fond of microscopic research who find a wide and interest- 

 ing field for their investigations in the anatomy, external and 

 internal, of this hitherto little known order. It occurred to us 

 then that a short account of a structure which, so far as we are 

 aware, has never been made special mention of before, though it 

 probably has not escaped notice, together with an account of its 

 use to the individual, and possibly minor importance in schemes 

 of classification, might be both welcome to the seeker after 

 curiosities for the microscope and general naturalist, as well as to 

 the more systematic student of the spider world. 



As to the tarsal appendages of spiders in general (the term 

 tarsal referring, of course, to the last joint of the legs), we might 

 remark that they consist of claws of various number, size, and 

 conformation ; some plain, others serrated or toothed on the 

 inner margins, all apparently specially adapted for the conditions 

 under which the owners thereof exist. As we should naturally 

 conjecture, those spiders which construct complicated snares 

 usually possess a higher development of the tarsal claws, specially 

 constructed for the seizing hold of lines, and the general manipu- 

 lation of tangled ropeage. The EpeiridcE (wheel-web spinners), 

 e.g.^ possess three tarsal-claws and several more subsidiary claws, 

 which they must find highly useful in handling their delicate lines. 

 The Agdenidce, another family constructing funnel-shaped, sheet- 

 like snares, also possess three tarsal-claws ; whereas the Drassidce, 

 a family whose members construct tubular retreats in holes and 

 crannies, rejoice in only two claws. The family DidynidcE possess 

 a further development in web-weaving apparatus, called the 

 calamistrum, the name given to a longitudinal series of stiff, 



