44 AMERICAN SPIDERS AND THEIR SPINNINGWORK. 
parent tube from which proceeds a thick thread. In its course it runs 
between the delicate external net like walls (n.w), which originated as a 
continuation of the ampulla, and terminate close at the base of the spin- 
neret. The walls are without ordinary cell formations. There is no dif- 
ference in construction between the cylindrical and ampullate part of this 
gland. Of the Treeform, or as Meckel denominates them Aggregate glands, 
tr.g, there are five on either side, of which four discharge at the anterior 
spinneret, and one at the middle. The secreting part of these 
glands consists of a large, white canal, widening into many sacs, 
which form together a roundish cluster, ¢, ¢, c. The duct, tr.d, 
runs quite close to the middle of the cluster, like the umbilical cord from 
the placenta in mammals. In the beginning it is straight and smooth, but 
farther on is accompanied on its superficial part by a number of small blind 
sacs (bs), with thin necks. 
Towards the end, the duct 
becomes smooth again, and 
enters the spool destined for 
it, which is somewhat larger 
than that of the cylindrical 
glands. Soon after its exit 
from the gland the duct has 
a diameter of 0.160 mm., 
but greatly narrows toward 
the spinneret to 0.04 mm. 
The duct appears, through- 
out its entire length, spiral- 
Fic. 36. Glands of Epeira diademata. (After Meckel.) cy.g, j A a 
Meckel’s cylindrical glands; am.g, ampullate glands; bl.g, bulbous ly twisted, without forming 
glands; py.g, cluster of pyriform glands leading into the spin- such folds as are seen in the 
neret, spn. - . 
cylindrical glands. 
Meckel further describes what he calls the Tuberose or Bulbous glands 
(glandule tuberosee), of which he says there is one on either side. (Fig. 36, 
bl.g.) According to this author they are small, and consist of a few branching 
tubes with knotted enlargements at short intervals, which pass finally into a 
duct that unites with the duct of the large cylindrical gland (Ventricose gland 
of Meckel), which leads into the middle spinneret. Bucholz and Landois, 
however, declare that they have never been able to detect this gland, and 
doubt its existence. I have seen somewhat similar glands in Argiope cophi- 
naria, but have simply regarded them as one of the various forms of the 
pyriform glands. 
A valuable study of the internal spinning organs of spiders was made by 
Mr. R. H. Meade, and reported to the British Association as early as 1844.1 
Treeform 
Glands. 
1 On some Points in the Anatomy of the Araneida or True Spiders, especially on the Internal 
Structure of their Spinning Organs, by R. H. Meade, F. R. C.8.; British Association Reports, 
1858, page 157, sq. 
