S. 
AMERICAN SPIDERS AND THEIR SPINNINGWORK. 
were uniformly eight, two of which were situated on the inferior surface 
of the spinneret at a greater distance from the extremity than the rest, 
and were minute and almost contiguous. 
It is a fact deserving notice that the spinning spools are not always 
developed simultaneously on these spinnerets, six, seven, and eight being 
sometimes observed on one, while five, six, or seven are to be seen on the 
other. This remark is applicable not to the anterior spinnerets alone, but 
to the intermediate ones also, which, in mature individuals, are further 
modified by having the extremities of the terminal joints directed forwards 
at right angles to their bases. The same condition was observed in a 
species of Drassus and in Segestria senoculata. It is not improbable, there- 
fore, that other species, and per- 
haps all spiders, follow the same 
law of development. 
This whole system of liquid 
silk supply is regulated by the 
compression of surround- 
ing muscles, which act 
upon the seyeral glands 
in the manner of the hand when 
squeezing upon the rubber bulb of 
a spraying tube. The contents are 
forced out of the glands in this 
liquid condition, through the long, 
delicate ducts, into the hollow spin- 
Fic. 46. Epeira diademata. sp (p), spigot of treeform ning tubes, whence they issue in 
isnt cn mattig (atten Thuusrniy’ erie pyrifor™ inute jets through the exterior 
openings or mouths of the spools. 
As the points of the spools or tips of the spinnerets are approximated, a 
number of these jets flow together, and hardening instantly upon contact 
with the air, form the thread or line familiarly known as the spider’s web. 
The excretory ducts, as well as the silk glands themselves, are encircled by 
a fibrous or muscular coat, which loosely surrounds them, and seems to be a 
continuation of the outer coat or sac itself. The spinnerets are connected 
with, or surmount the integument of the abdomen, by means of diverging 
bands of muscular fibres, which enable them to move in different directions. 
These muscles are placed immediately beneath the skin, and their expanded 
extremities are inserted into it so that they -are separated with it, unless 
dissected very carefully.? 
All the spinnerets are thus provided with many muscles which cause 
the approachment of all the spools of one spinneret against one another, 
as also the convergence of all the six spinnerets towards a central point, 
in order to produce in this way a single thread. For this purpose the 
1 Meade, 
Muscular 
System. 
h « 
