SPINNING . APPARATUS OF GEOMETEIO SPIDERS. 63 



morphology of the organs in question will be necessary. The 

 large garden spider, Epeira diadematajis taken as the most 

 convenient type of the family, but the following remarks apply 

 in the main to all its orb-weaving congeners. 



External Spinning Organs. 



These occupy a small round area on the under surface of the 

 abdomen towards the posterior end, where, when at rest, they 

 present a bluntly conical protuberance (figs. 1 and 2, sp.) . If 

 this area be examined under a low power, it is seen to be 

 occupied mainly by four conical spinnerets, their bases form- 

 ing a quadrilateral, and their apices meeting in the centre of 

 the area (fig. 8). The narrow space which intervenes between 

 the bases of the anterior (or inferior) spinnerets (a) is filled by 

 a small tongue-like process {t). The wider gap separating the 

 posterior (or superior) spinnerets (p) is occupied by a terminal 

 projection of the abdomen (z) containing the anus. Each of 

 these spinnerets is two -jointed, and furnished at its extremity 

 with a multitude of hair-like tubes containing the ducts of the 

 spinning glands. 



They are possessed of a wonderful mobility, and can be 

 widely separated, or energetically rubbed upon each other with 

 a rotary motion at the will of the animal. Their separation 

 discloses a third and smaller pair of spinnerets consisting of 

 one joint only, and having their apices directed backwards and 

 inwards, so as to lie immediately beneath the apices of the 

 posterior spinnerets (fig. 10, i). 



These again present a large number of glandular orifices. 

 They will be referred to hereafter as the intermediate spinnerets. 

 Thus we have, in all, three pairs of spinnerets capable of a great 

 variety of movement, and bearing at their extremities, as will 

 be presently seen, about 600 spinning tubes. 



Internal Spinning Organs. 

 Apstein has shown that there are, in this group of spiders, 

 five distinct kinds of glands, to which he assigns the names 

 Ampullaceal, Aggregate, Tubuliform, Piriform, and 



