THE SPINNING ORGANS. 



43 



tr.g- 



- tu 



Py.gr-- 



b.du 



SF 



FIG. 35. Three forms of spinning glands opening into the posterior spinneret, spn. The middle one 

 enlarged in different proportion from the others, py.g, a group of pyriform glands, b.du, a bundle 

 of ducts opening into the spinneret through the spinning field, SF. tr.g, treeform gland ; tr.d, 

 excretory duct with brownish glandular walls or boundaries, bs ; cy.g, cylindrical gland ; tu, its 

 tubular part ; am, ampullate expansion of the same ; b.du, beginning of duct from the ampulla ; 

 c.du, cylindrical duct ; do and k, the noose shaped twist of the duct continued in an external 

 envelope, n.w, derived from the ampulla. 



