The external spinning-organs are little two-jointed tubes on the ends of the spinnerets, Fig. 1, L. Fig. 16 is the spinnerets of the same spider, still more enlarged to show the arrangement of the tubes. There is a large number of little tubes on each spinneret, and in certain places a few larger ones. Fig. 17 is a single tube, showing the ducta which leads the viscid liquid to form the thread from a gland in the spider’s abdomen. Each tube is the outlet of a separate gland. Fig. 18, _a_, shows four small tubes from a spinneret of _Epeira_, each with a small gland attached; and Fig. 18, _b_, a large tube, with one of the large glands which extends forward the whole length of the abdomen, Fig. 5, _u_. [Illustration: Fig. 17.] [Illustration: Fig. 18.] The shape of the spinnerets, and size and arrangement of the tubes, vary in different species. Fig. 19 is a spinneret of _Prosthesima_, where there are a few large tubes in place of many small ones. In _Agalena_ the two hinder spinnerets are long, and have spinning-tubes along the under side of the last joint, Fig. 20. When the spider begins a thread, it presses the spinnerets against some object, and forces out enough of the secretion from each tube to adhere to it. Then it moves the spinnerets away; and the viscid liquid is drawn out, and hardens at once into threads,—one from each tube. If the spinnerets are kept apart, a band of threads is formed; but, if they are closed together, the fine threads unite into one or more larger ones. If a spider is allowed to attach its thread to glass, the end can be seen spread out over a surface as large as the ends of the spinnerets, covered with very fine threads pointing toward the middle, where they unite, Fig. 21. [Illustration: Fig. 19.] [Illustration: Fig. 20.] The spinning is commonly helped by the hinder feet, which guide the thread, and keep it clear of surrounding objects, and even pull it from the spinnerets. This is well seen when an insect has been caught in a web, and the spider is trying to tie it up with threads. She goes as near as she safely can, and draws out a band of fine threads, which she reaches out toward the insect with one of her hind-feet; so that it may strike the threads as it kicks, and become entangled with them. As soon as the insect is tied tightly enough to be handled, the spider holds and turns it over and over with her third pair of feet, while, with the fourth pair, she draws out, hand over hand, the band of fine threads which adhere to the insect as it turns, and soon cover it entirely. [Illustration: Fig. 21.] It is a common habit with spiders to draw out a thread behind as they walk along; and in this way they make the great quantities of threads that sometimes cover a field of grass, or the side of a house. We often see the points of all the pickets of a fence connected by threads spun in this way by spiders running down one picket, and up the next, for no apparent purpose.