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38 II. DE ARACHNIDIS<br />
4. PHYSIOLOGY: II'\TER:KAL ORGANS 39<br />
m IV V<br />
i<br />
~---- -------~------------~------------- --------- _,--,___<br />
ii<br />
FIG. 11. i\ervous system of a spider.<br />
This is regarded as the more primitive method. In some orders it<br />
has been replaced by adapting a limb for conveying the sperm: the<br />
pedipalpi in Araneae, the third leg in Ricinulei. Lastly, there may be a<br />
real intromittent organ and copulation in the true sense may occur, as<br />
in the Opiliones and some Acari.<br />
Three distinct methods of excretion are found among <strong>Arachnida</strong>,<br />
the most fully developed of which is the system of coxal glands (Figs 13<br />
and 14). In their typical form, many modifications of which are,<br />
however, found, they consist of a large excretory saccule, lined with<br />
---------~- -------~--------~iii<br />
--------~-<br />
FIG. 13. Coxal glands. (i 1 Scorpiones; >-\mblyjlygi; (iiii >\mbly;Jygi !Charontini!;<br />
Uropygi; (v', Pal;'igradi.<br />
FIG. 12. Diagram of female reproductive organs of a spider. A, ovary; B, oviduct; C,<br />
spermatheca; D, orifice for entry of sperm; E, vagina.<br />
cubical or flattened epithelium, lying outside the cndosternitc opposite<br />
the coxae of the first legs. This discharges its products into a eo m oluted<br />
tube, the labyrinth, the coils of which occupy the space from the first to<br />
the fourth coxa, or beyond. At the distal end of the labyrinth there is<br />
sometimes a S\n·lling, rt>garded as a "bladder". and from this there runs<br />
forward a straight tube, the internal limb of the labyrinth, which lies
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