XIII SPINNERETS 3 
i) 
ut 
Under considerable magnification the legs of all Spiders 
exhibit a number of minute organs, arranged with absolute 
uniformity throughout the Araneae,and known as the “lyriform 
organs.” They consist of little parallel ridges of thickened 
chitin, the sht between them being covered by thinner chitin. 
They are eleven on each leg, and are distributed near the distal 
extremities of each of the first. six jomts. Their function is 
unknown, though some authors consider them to be organs of 
hearing. 
The Spinnerets are normally six in number, and, except in 
rare instances, are placed beneath the abdomen, near its apex and 
immediately in front of the anal tubercle. 
Their arrangement varies greatly, but 
they can generally be recognised as 
comprising three pairs, a posterior (or 
superior) pair, a median pair, and an 
anterior (or inferior) pair. 
In nearly all the Theraphosae the 
anterior pair are absent, while the 
posterior spinnerets are largely de- 
veloped. In the Palpimanidae only 
the anterior spinnerets are present. 
When all six are found, the usual 
arrangement is in the form of a rosette, 
the median spinnerets being hidden by 
the others in repose, but this disposition 
is widely departed from. In Hahnia 
(Agelenidae), for instance, they are 
ranged in a transverse row at the end 
of the abdomen, the posterior spinnerets 
occupying the extremities of the row, 
and the median ones the centre. 
These spinnerets are highly mobile »,, 181, spinnerets of Hpeira 
appendages, and additional play is given — diademata. A, Ventral view 
to their action by the presence of articula- Cae o ee 
gnified ; C, : 
tions, much resembling the “ false ” joints 
sometimes found on the legs, on the posterior and anterior pairs. 
They are always at least bi-articulate, and sometimes present 
three or four joints. They are movable turrets on which are 
mounted the “fusulae ” or projections where the tubes from the 
