646 THE POPULAR SCIENCE MONTHLY. 



again and again, until successful. If it holds, she attaches her end 

 firmly by pressing her spinners upon the wood, so as to include the 

 line. The first and most important step in the construction of all 

 geometrical nets has now been taken, and the spider can meet with no 

 serious difficulty in completing her task. 



But the following steps might be taken in more than one way, and 

 perhaps are so at different times, or by different individuals. And, in 

 view of the risk of making inferences as to the habits of animals, I 

 refrain from the description of what may occur, and simply state that 

 in some way the spider connects with the original horizontal line four 

 others, constituting respectively the base-line (_B J3) of the net, and 

 the three lower radii (R" R" R"") which are joined to the base-line 

 at JF 1 , G, and H. The upper radius (R') is formed from the central 

 part of the original line, and the three others unite with it at A, the 

 apex of the triangular net. (See Figs. 1, 8, 9.) 



The framework of the net is now ready, and the spider begins to 

 construct the more essential part of its snare. 



The organs directly concerned in the operation are the hinder pair 

 of legs and the spinning mammulae, or spinnerets. 



The fourth pair of legs have, upon the last segment but one, a 

 series of strong and curved spines, forming a rake with teeth finely 

 set. When used, this rake appears to be carried backward over the 

 spinnerets, so as to draw out the silken threads. 



It seems to represent the calamistrum of the other Ciniflonidce, but 

 has no such effect, as with them, as to form a flossy border upon the 

 silken thread. 



Fig. 6. View of the Spinning Apparatus of Hyptiotes Americanns, from below and 



in Front. 



A, the lower surface of the abdomen ; v, the vent or outlet of the intestine, opening through a 

 papilla; a, one of the anterior pair ; p, one of the posterior pair; m, of the middle and 

 smaller pair; x, a low oval projection just in front of the spinners, which seems to correspond 

 to the fourth pair in other species; s s, the silk from the anterior spinners, uniting to form one 

 line, but capable of drying so as to form the two strands of the double interradial. I do not 

 know from which spinners the various parts of the net are formed. 



The spinning mammulce, or spinnerets, are represented in Fip;. 6. 

 They form a little group upon the lower surface of the abdomen, near 

 its hinder end. In a state of rest, they are closely approximated, but 

 when in use they are more or less widely spread apart like so many 

 fingers or short legs. Indeed, there is reason to regard the spinners as 



