322 ARACHNIDA—-ARANEAE CHAP. 
which assist in retaining the juices expressed by the chelicerae, 
and its anterior border presents a cutting edge with a finely 
dentated ridge called the “ serrula.” 
In the female, and in the immature male, the remaining 
joints differ little from those of the legs, except that the tarsal 
joint is either clawless or has a single claw, which is generally 
smooth, and is never much dentated. 
At the last moult but one the male pedipalp appears tumid 
at the end, and after the last moult the tarsus is seen to have 
developed a remarkable copulatory apparatus, the “ palpal organ,” 
comparatively simple in some families, but in others presenting 
an extraordinary complexity of structure. 
Palpal Organs.—Externally the essential parts of the palpal 
organ are three, the “ haematodocha,” the “ bulb,” and the “style.” 
The spines and projections, or “ apophyses,” which often accom- 
pany the palpal organ proper, are of secondary importance, and 
in many spiders are entirely absent; nor is their function when 
present at all clear; but 
the infinite variety of 
design which they ex- 
hibit, and their singular 
uniformity in all the 
males of a species, render 
them of the utmost value 
as specific characteristics. 
The “ haematodocha ” 
is the portion of the 
palpal organ attached to 
the tarsus, and often re- 
Fic. 179.—Diagram of palpal organ. 1, Tarsus ; ceived into an excavation, 
2, bulb ; 3, receptaculum seminis; 4, its aper- the “ alveolus,’ on _ its 
ture ; 5, style; 6, haematodocha ; 7, alveolus ; . 
8 tibia. under surface. It is a 
fibro-elastic bag, in its 
normal collapsed state usually somewhat spirally disposed round 
the base of the following portion, the “bulb.” 
The bulb is generally the most conspicuous portion of the 
organ, and is a sub-globular sac with firm, though often semi- 
transparent, integument. Its base rests upon the haematodocha, 
and its apex is produced, often spirally, to a point which bears 
the seminal orifice. This external opening leads into a coiled 
