fal AMERICAN SPIDERS AND THEIR SPINNINGWORK. 
X. 
The poison glands after the first moult are situated with Attus in the 
mandibles, and do not pass beyond those limits. Further on, as with 
: the Lycosid (Trochosa), the inferior end of the gland is placed 
eae rather below the median line of the mandible. (Fig. 71, gly.) 
Afterwards the superior parts of the gland issue beyond the 
mandible for a third of their length (Fig. 72), and their inferior extremi- 
ties do not reach the median line of the mandible. Finally, after a series 
of moults, the gland is no longer found within the mandible, but extends 
wholly beyond it (Fig. 78), and is withdrawn farther and farther with 
every moult. At the same time the dimensions of the gland increase as 
well as the number of muscular fibres; a fact which gives us a measure 
of the phylogenetic development of any spider thus tested. 
With the genus Epeira the poison glands are relatively large. They are 
placed in the anterior part of the cephalothorax at some distance from the 
mandibles, with which they are joined 
bionide these glands are of a much 
smaller size than with Epeira, and only 
a part thereof is found within the ceph- 
alothorax, the remainder of the gland 
being situated within the basal joint of 
the mandible. With the Mygalide the 
whole gland is located with- 
in the basal joint. It will 
thus be seen that the modi- glv- 
by quite a long conduit. With the Clu- 
fications in the poison gland 
accomplished by successive em who. 7, 
moults in advancing age gona 
are, first, the increase in MOULTING OF PoIsON GLAND IN TROCHOSA. 
Be Fic. 71. Venom gland, gl.v, at an early stage, inside the mandible; 
8128, and, second, the change er, the duct. Fia. 72, Gland at further stage. Fie, 738, Gland 
of position. after final moult, withdrawn beyond the mandible. 
A study of the rejected moult of a spider shows well the thickened 
points of insertion of the muscles of the abdomen, which in that organ 
_ are, characteristically, immediately upon the cuticle. Upon the 
Abdomi- inferior or ventral part of the abdominal moult, according to 
nal Mus- ; 3 ; nabs 
Aaa Wagner, there are two median rows of thickenings, consisting of 
sixteen pairs, a little removed from one another (Fig. 74, Nos. 
1-16); then two rows of lateral thickenings. (Fig. 74, Nos. 17-39.) These 
rows consist of twenty-three pairs of thickenings disposed first (near to the 
lungs) irregularly, and then in lines almost straight and parallel to the 
two medians. In all, there are on the inferior face of the abdomen thirty- 
nine pairs of thickenings, representing the points of insertion. Besides 
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