THE SPINNIXG ORGANS. 



43 



b.du' 



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, SK. tr.g, treeform gland ; tr.d, 

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

 tubular part ; am, ampuUate 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. 



