The External Anatomy of Spicier. 



ex -a.. 



The terminal apophysis is modified into an organ for the support of the emh< 

 I I r ig. i 14. ful.), which may be termed the fulcrum of the embolus. I his type of 

 terminal apophysis has been termed, incorrectly, the conductor. The true coi 

 ductor in this species, as in all others studied, is an organ whose function is to 

 protect the tip of the embolus in the unexpanded bulb. At the base of the terminal 

 apophysis, at the point where the embolus arises, there is a lamelliform lateral 

 subterminal apophysis (Fig. 1 14, st. a.). 



In the unexpanded bulb (Fig. 1 1 5), the long embolus makes a cun e in 1 In- distal 

 end of the alveolus beyond the end of the bulb. The fulcrum is applied against 

 the embolus on its concave side, and has a 

 furrow on its distal face within which the 

 embolus rests. The distal part of the conductor 

 is wrapped about the tip of the combined 

 embolus and fulcrum, serving, as in all other 

 cases observed, as a protection to the tip of 

 the embolus. 



The Thomisid Type of Palpus. — In the 

 family I homisidae, there occurs a striking 

 modification of the palpus, which consists of the 

 absence of the conductor of the embolus and, 

 in certain members of the family, of a special- 

 ization of one edge of the cymbium for the 

 protection of the tip of the embolus in the 

 unexpanded bulb. To this specialized part cf 

 the cymbium 1 have applied the term tutaculum 

 (tu-tac'u-lum); it is described and figured in the 

 general account of the Thomisidae on a later 

 page. It is best developed in the genus 

 Xysticus. 



The Anelli of the Subtegulum. — In 

 Aranea, the chitinized part of the wall of the 

 basal division of the bulb, the subtegulum, is 

 reduced to a ring-like sclerite (Fig. 1 16, 1.); but 

 in certain other genera, the subtegulum is cup- 

 shaped or basket-like. In Agelena navia (Fig. 

 1 16, 2.), one side of the 

 subtegulum is greatly 

 thickened; at the prox- 

 imal end of this thicken- 

 ing, which corresponds 

 to the lunate plate, 

 t here is a condyle, which 

 articulates with the pet- 

 iole; and at the distal 

 end, there is a condyle, 



which articulates with the tegulum. The other side of the cup-like subtegulum 

 contains in its wall several parallel, incompletely ring-like sclerites; these may 

 be termed the anelli of the subtegulum. In Dolomedes fontanus (Fig. ii<>. 

 the anelli of the subtegulum are greatly thickened and form prominent, 

 projecting ridges. 



It is probable that the presence or absence of the anelli of the subtegulum, 

 and their nature when present will atford characters of use for taxonomic purposes 



The Different Types 01 Embolus.— 1 he form of the embolus \ aries greatly 

 in dilferent species of spiders. Two principal types can he recognized, the connate 

 and the free; and the free type includes three subtypes. 



The connate type of embolus. — In the connate type, the embolus is not separate 

 from the middle division of the bulb, hut is merely a more slender continuation 

 of it, as in the tarantulas. Loxosceles (Fig 96), and l-nulna. 



The tree type of embolus. — In the free type "t embolus, there an- one or p 

 movable articulations between the embolus and the middle division of the bulb 



Fig. 115. UNEXPANDED BULB 



OF DOLO.MKDKS FONTAN1 - 



Fig. 116. THREE KINDS OF SUBTEGULl M 



I K) 



