THE SPENDING ORGANS. 



35 



su 



about equal in length. In form these organs are somewhat conical and 

 cylindrical, widened at the base and gently sloped or flattened at the tips. 

 The three pairs differ somewhat in appearance and size, the mid- 

 16 pm "dle pair being shorter and less in size and more closely approx- 

 imated. The posterior and anterior spinnerets have two joints 

 (Bucholz and Landois); the middle ones are unjointed cones. 1 They are 

 movable, particularly the posterior and anterior pairs, articulating with the 

 integument of the body, and can 

 be closed in upon each other until 

 the tips touch at the spinning fields, 

 as when one closes the thumb upon 

 the four fingers of his hand. The 

 spinning fields, Fig. 21, SF, are 

 those portions of the tips and sides 

 of the spinnerets on which are 

 placed the sessile tubes out of 

 which the silk passes. 



In repose the spinnerets are gen- 

 erally closed (Fig. 21), forming a 

 sort of rosette of five divisions; but 

 when the spider is engaged in ac- 

 tive operations, the posterior and 

 anterior spinnerets are thrown well 

 back, and the two middle 

 1. Poste- ones O p n U p ? an( j thus, 

 rior Spin- ,, , * 



nereis to ( * UOt the lan g ua S e of 

 Dugds, " this singular flow- 

 er unfolds." The posterior spinner- 

 ets (Figs. 21 and 23, P) 2 are well 

 separated from each other, and lie 



directly forward Of the Semilunar FIG. 23. Posterior spinneret of Ep. diademata, greatly 



i f-rt- cti \ mi. magnified, su, sutine between joints; SF, spinning 



anal Covering (llg. 21, ac). Ihey field; bb) branched bristles; sb, simple bristles; sp, 



are movable horizontally toward spigot spool; l.ss, long spinning spools; s.ss, short 



, ,1-1 i spools. (After Bucholz and Landois.) 



each other, so that their long oval 



spinning fields approximate and, indeed, may be said to lie upon the cor- 

 responding middle spinnerets. They may be described as thumb shaped 

 organs; are of a long, cylindrical form, and towards the free end are con- 

 ically rounded. The terminal joint is divided from the base by a suture, 

 Fig. 23, su, which extends along the inner and hinder edge, much farther 

 than on the opposite edge, so that the spinning field extends on that face 

 much farther towards the base. 



1 Meckel, and Oeflinger both attribute three joints to the posterior and anterior, and two 

 to the middle spinnerets. 



2 To prevent confusion and the multiplication of references to figures the same letter 

 ing is preserved for like organs and parts thereof in all the anatomical figures. 



