THE SPINNING ORGANS. 39 
They are placed in a mass just above the spinnerets, and within their 
bases and the abdomen, and along the venter forward and laterally. See 
Fig. 30. The pyriform glands, which are smaller and very much the most 
numerous, are arranged in five roundish clusters, about two millimetres in 
diameter in A. cophinaria, each corresponding to ‘one of the exterior spin- 
: nerets, one cluster being devoted to the two middle spinnerets, al- 
Sill though even in this case the clusters can be separated into two. 
Glands: ; 5 
Number, Lhe number of glands precisely corresponds with the number of 
spinning spools and spigots. Bucholz and Landois give about 
seven hundred for Epeira diademata and they are as numerous in Argiope 
cophinaria. Mr. Blackwall expresses the opinion that the total number of 
spinning spools does not greatly exceed a thousand, even in adult females 
of Epeira quadrata, whose weight is about twenty grains, and in many other 
species it is smaller. As the spools correspond in number with the glands, 
this gives an indication of the number of silk glands within our best known 
<i oe 
“spn 
: i By 
ep trg cy-g py2 
Fic. 30. Partly diagramatic view of the location of the spinning organs in Argiope 
cophinaria. spn, spinnerets; py.g, pyriform glands; cy.g, cylindrical glands; tr.g, 
treeform glands; ep, epigynum; gl, gills: E, eggs; al.c, alimentary canal; a, anus. 
Th figure is a composite one. 
Orbweayers. Each gland terminates in a long, delicate duct, and one duct 
enters one of the spools; a distinct duct belongs to every spool, without any 
connection, as a rule, with other ducts or glands. 
Under the microscope the liquid silk can be seen very distinctly within 
the glands, and presents the appearance of minute, yellowish, translucent glob- 
ules of thickish oily or viscous substance. Some of the glands of Argiope 
cophinaria appear to contain material which is rather smoother and of a 
lighter color than that above described. The contents of some 
glands in this species have a reddish brown color, which indicates 
that they supply the brown silken padding that envelops the 
eggs of this species and lie just within the outer cocoon case. Where the 
glands have been broken, or the contents spilled on the mounting cover, the 
liquid silk generally shows stringy or fibrous, but sometimes maintains the 
globular appearance retained within the gland. It is very probable that 
Liquid 
Silk. 
