THE SPINNING ORGANS. 



37 



s.ss 



.sp.c 



The spinnerets articulate 



obliquely from the outer side 



and the front, inward and 



backward, so that their tips 



approximate the corresi)ond- 



ing spinning fields of the mid- 

 dle spinnerets. The base is 



covered on both of its side 



faces with many rows of bris- 

 tles (Fig. 25, b) ; it is divided 



from the terminal field by a 



suture, su, and a brown chit- 



inous zone, z. The terminal 



joint is cap-shape, and is only 



partially occupied as a spin- 

 ning field. 



On the top of the spinning 



field are from sixty to seventy 



very short spinning spools, 



S.SS, and a spinning spigot, 



connected with a cylindrical 



gland, Fig. 25, sp.c. The base 



of these spigots is surrounded 



by a pair of chitinized stripes, 



which originate in the ehit- 



inous zone, z. Close to this 



place is inserted a very strong 



and long sinew, sw, which unites witli the chitinous border of the spin- 

 ning field at the furrow (su) between the base and the terminal joint. 



This sinew passes beyond the root of the spinneret into the strong, motor 



muscle, ms, which controls the movement of 

 the spinneret towards its fellows. Within the 

 bases of the spinnerets are bundles of muscles 

 which contribute both to the general move- 

 ment of the spinneret and to the movement 

 of the individual spools on the tip. On the 

 chitinous edge of the spinning field is a single 

 row of strong bristles, br. 



On examining the spinnerets with a lens 

 of ordinary jiower, the tips or spinning fields 

 are found to be covered with a great number 

 of fine movable spinning tubes, already men- 



clusters. a, short spools ; c, long spools ; t^iQi-^^.^] knOWn aS Spinning Spools (Fig. 26), 

 b, a small cluster; tj, terminal joint; , , t ^ ,i <■ 



bj, basal joint. wliicli are regularly disposed over the surface. 



Fig. 25. Anterior spinneret, magnified largely, z, brown chit- 

 inous zone that bounds the spinning field ; sw, sinew of the 

 bending muscles of the anterior spinning wart ; du.c, duct 

 from cylindrical spinning glands ; sp.c, spigot discharging cy- 

 lindrical gland ; sp.t, spigot of treefonn gland ; s.ss, spinning 

 spools of pyriform glands. (Bucholz and Landois.) 



Fig. 26. View of the spinning spools of 

 Argiope cophinaria, as they appear in 



