326 



ARACHNIDA ARANEAE 



spinning glands open. These are often very numerous, especially 

 in the orb-weaving spiders, where the spinning powers are most 

 highly developed. They consist of two portions, a cylindrical or 

 conical basal part, succeeded by a very fine, generally tapering 

 tube. 



In some spiders the fusulae are all much alike, but usually a 

 few very much larger than the rest are noticeable under the 

 microscope, and these are often alluded to as " spigots." The 

 smaller ones are also divisible into two kinds, a few short conical 

 fusulae being noticeable amongst the much more numerous 

 cylindrical tubes. We shall treat of the functions of the various 

 fusulae later (see pp. 335 and 349). 



Simon remarks that though the battery of fusulae is most 

 complicated in those spiders which possess the greatest spinning 

 powers, it is by no means among them that extremely long 

 spinnerets are developed. The posterior spinnerets of some of the 

 Hersiliidae are of great length, but these spiders spin very little 

 except in forming their egg-cocoons. 



In addition to the six spinnerets, and just in front of them, 

 there is to be found in some spiders an extra spinning organ in 



the form of a 

 double sieve-like 

 plate, the " cri- 

 bellum." This 

 is always corre- 

 lated with a 

 comb of curved 

 bristles on the 

 metatarsi of the 

 fourth pair of 

 legs, the " cala- 

 mistrum." Such 

 importance is 



FIG. 182. A, Spinnerets of Amaurobius similis $. Much assigned to these 

 enlarged, a, Anus ; cr, cribellum ; i.s, inferior spinneret ; 



m.s, median spinneret ; s.s, superior spinneret. B, Part of Organs by SilUUIl, 



the 4th leg of the same Spider, showing the calaniistrum (c) fU f f 1 1C1 A ,.. 



on the metatarsus. tllat tl16 A ne ^ e 



Veraeare divided 



by him according to whether they are present or absent, 

 into CRIBELLATAE and ECRIBELLATAE. This is probably an 

 exaggerated view of the importance of these organs, and the 



