STRUCTURE AND ECONOMY OF SPIDERS. 321 
hibit. Arranged along the underside of the terminal 
joint, they present the appearance of fine hairs dilated 
at the base projecting from it at right angles ; but if 
the spinners, when they are in operation, be carefully 
examined with a powerful magnifier, the function of 
the hair-like tubes may be ascertained without diffi- 
culty, as the fine lines of silk proceeding from them 
will be distinctly perceived. 
In conducting this observation I usually employ 
the <Agelena labyrinthica of M. Walckenaer—partly 
because I can procure specimens with facility ; but 
chiefly on account of its size, the length of its supe- 
rior mammule, and its habits of industry, affording 
a combination of advantages comprised by no other 
British spider (see Plate II. fig. 2). 
The purpose subserved by the superior mammule, 
when very prominent and composed of several joints, 
is the binding down with transverse lines, distributed 
by means of an extensive lateral motion, the threads 
emitted from the inferior mammule ; by which pro- 
cess a compact tissue is speedily fabricated. 
The foregoing facts supply a striking exemplifica- 
tion of the importance of connecting physiological 
investigations with anatomical details. 
Not being aware, apparently, of the publication of 
the discovery in the ‘ Report of the Third Meeting of 
the British Association for the Advancement of 
Science, held at Cambridge in 1833,’ p. 445, Baron 
Walckenaer, in the supplement to the second volume 
Y 
