194 THE SPIDERS OF EPPING FOREST.
three in number, and in some species a number of minute supernumerary
claws are found, opposed to the ordinary ones. The eyes are sometimes
heterogeneous and sometimes homogeneous, in that case being of the diurnal
type. In some species the caput of the male is elevated in a most remarkable
manner, several of the eyes being often placed upon the raised portion. The
development of the tarsus of the male palpus from the simplest forms to the
most complex is very curious and interesting. Instead of the joint being
modified by a hollowing process to receive the palpal organs, it is split longi-
tudinally, this structure being very clearly seen in Pachygnatha, the, genus
from which apparently the argiopiform spiders have developed. In this
case we find both branches of the split joint very distinct and between them
the bulb of a very simple form and provided with but few appendages. From
this genus we can trace four distinct lines of development. The first series,
developing through Tetragnatha and Meta, gives rise to orb-spinning spiders
such as those of the genus Aranea and, possibly, the cribellate family
Uloboridae. The second terminates in the spiders of the "Walckenaera"
type, the males of which possess, as a rule, curious cephalic prominences and
tibial apophyses upon the palpi. The third tends towards the higher types
of the "Linyphia" group with well developed spines upon the legs and highly
complex palpal organs. From the fourth we may trace the Theridiids, with
the aberrant family Pholcidae. With the structural development of these
various types the palpus has undergone great modifications, notably in the
gradual elimination of the external branch of the tarsus. The remaining
branch (i.e. the internal one) often becomes of a cup-shaped form, reminding
one strongly of the palpal tarsus of some of the Drassiform spiders, but with
the most important difference that the palpal organs are placed upon the
external surface of the joint instead of upon its under side. The palpal
organs, too, are usually far less enclosed by the tarsus than in the Drassi-
formae, the joint being often reduced to very small portions. The modified
external branch of the divided tarsus is found in several groups of Argiopi-
form spiders. It is rather conspicuous in many of the representatives of the
sub-family Linyphiinae of the family Linyphiidae and has been often referred
to under the term "falciform process.''
The Argiopiformae are for the most part deprived of tibial apophyses,
but in some groups, notably the sub-family Erigoninae these structures are very
strikingly developed. They are, however, of a form very different from that
exhibited by the Drassiformae. In the first place they are not nearly as
distinctly defined, being, as a rule more or less of the nature of expansions of
thejoint itself, thus rendering it in many cases a matter of some difficulty to
decide exactly where the joint terminates and the apophysis commences.
Their position, also, is very characteristic, for they are usually placed upon
the superior anterior portion of the tibia, projecting considerably over the
tarsus and thus precluding any great vertical motion of the joint. The
lateral motion, necessitated by the external placing of the organs, is thus in
no way impeded. The genital aperture of the female, except in a few primi-
tive types, is furnished with epigynal plates, and often with a clavus also.
The Argiopiformae almost invariably fabricate some form of snare. In
the majority of cases it consists of a horizontal sheet of irregular threads