The External Anatomy of Spiders 



but is different in some details. It is figured here to illustrate the kind of varia- 

 tions in form that serve to distinguish closely allied species (Fig. 107). The 

 median apophysis differs markedly in form from that of A. frondosa; the tegulum 

 bears a small but distinct apophysis; the lateral subterminal apophysis bears two 

 prominent teeth; and the terminal apophysis is lacking, the embolic subdivision 

 ending in a blunt lobe. 



The Palpus of Eriophora Circulata. — The most striking modification 

 of the aranea type of palpus, taking the palpus of Aranea frondosa as typical, is 

 that of Eriophora circulata, which is the most complex palpus that i have studied. 

 In the unexpanded bulb, there appears to be no resemblance to the bulb of Aranea 

 frondosa. In Eriophora circulata (Figs. 108 and 109), the bulb is very large and 

 the cymbium comparatively small and narrow (Fig. 109, cym.). The basal hzema- 

 todocha (Fig. 108, b. h.) is conspicuous, which is a result of the other parts of the 

 bulb being twisted into unusual positions. The median apophysis is large and 

 projects beyond the tip of the bulb (Fig. 108, m. a.). But the most remarkable 

 feature is an elbowed structure on the mesal aspect at the base of the bulb (Fig. 

 109). The fact that the ejaculatory duct can be traced throughout the length of 



this elbowed structure gave the first 

 definite clue to the relations of the 

 -emb. parts of the bulb. The part contain- 

 ing the ejaculatory duct evidently 



Wt.a. 



jnl »i. st. a. 

 1 



m.a.-- 



Fig. in. EXPANDED BULB OF 



ERIOPHORA CIRCULATA 



Fig. 112. UNEXPANDED BULB OF 

 \KA.\EA GIGAS 



pertains to the apical division of the bulb, although it appears to arise from the 

 base of the bulb. 



When the bulb of Eriophora circulata is expanded and untwisted, as occurs 

 in the process of expansion, the relations of the parts are more easily seen. Figures 

 1 10 and 1 1 1 represent two views of a preparation of this kind. If Fig. 1 1 1 be 

 studied it will be seen that the relations of parts are essentially the same as in 

 Aranea frondosa (Fig. 106); the basal ha;matodocha, subtegulum, and tegulum 

 follow in the same sequence; the median apophysis and the conductor project from 

 beneath the tegulum in the corresponding positions, and the elbowed structure, 

 which in the unexpanded bulb appears to arise at the base of the bulb is here 

 clearly seen to be the embolic subdivision of the bulb. I he most remarkable 

 differences are the lack of a prominent distal ha*matodocha and the fact that 

 the radix (Fig. 111, ra.) and stipes il ig, in, st.) are each .1 complete cylinder, 

 instead of merely forming one face of the wall of .1 segment of the apical division, 

 as in Aranea frondosa. At the distal end of the stipes, between this part and the 

 embolus and the terminal apophysis, thfere is a vestigial distal h.ematodocha 

 (Fig. 110, d. h.). 



I I 



