THE TRIANGLE SPIDER. 647 



corresponding in essential structure with the true legs of the spider. 

 They are jointed or articulated, and capable of considerable move- 

 ment. Their number and form vary with different genera. In our 

 spider there are three pair, anterior (a), middle (m), and posterior (p). 

 The middle pair are smaller, and ordinarily concealed by the others. 

 Behind the spinners is the median papilla through which opens the 

 vent (). In front of them is a low, broad, oval-topped papilla (x), in 

 which I find no trace of division into two, nor any silk-tubes. It 

 probably represents the fourth pair of spinners, which exist in the 

 other Ciniflonidce. 



The tips of the spinners are provided with many little tubes, hav- 

 ing the appearance seen in Fig. 7. Through these is drawn the gum 



Fig. 7. A Single Silk-Tube from the End op an Anterior Spinner. 



secreted by the silk-glands within the abdomen, and all the strands 

 from a single spinner may combine to form a single thread. 



It is probable that the different pairs of spinners are supplied from 

 different glands, and that they are enrployed in making different parts 

 of the net. With the Nephila plumipes, 1 I found that from one pair 

 came only white silk, while another pair produced only yellow. By 

 separating these with pins, soon after leaving the body, and attaching 



1 For an account of this species, and of the JSpeira riparia, see the following papers : 



" On the Nephila plumipes, or Silk-Spider of South Carolina " (" Proceedings of the 

 American Academy of Arts and Sciences," November, 1865). 



" On the Nephila plumipes " (" Proceedings of the Boston Society of Natural History," 

 October 4, 1865). 



" On the Silk-Spider of South Carolina; Four Lectures before the Lowell Institute, 

 March, 1866 " (unpublished). 



" How my New Acquaintances spin " (Atlantic Monthly, August, 1866). 



"Memoirs of a Cripple" (Our Young Folks, September, 1866). 



"Researches and Experiments upon Silk from Spiders " (Termeyer, 1810-1820?) 

 edited by B. G. W., and published in the "Proceedings of the Essex Institute," Salem, 

 Mass., July 6, 1874. 



"Two Hundred Thousand Spiders" (Harper's Magazine, March, 1867). 



" The Practical View of Spider's Silk " (The Galaxy, July, 1869). 



" The Habits and Parasites of JSpeira riparia " (" Proceedings of the American Asso- 

 ciation for the Advancement of Science," 1873). 



' The Nets of JSpeira, Nephila, and Hyptiotes (Mithras)." (Ibid.) 



