xi SPINNING GLANDS 335 
Spinning Glands.—Spiders vary greatly in their spinning 
powers. Some only use their silk for spinning a cocoon to pro- 
tect their eggs, while others employ it to make snares and _ re- 
treats, to bind up their prey, and to anchor themselves to spots to 
which they may wish to return, and whence they “drag at each 
remove a lengthening chain.” 
All these functions are performed by the silk-glands of the Orb- 
weavers, and hence it is with them that the organs have attained 
their greatest perfection. We may conveniently take the case of 
the common large Garden-spider, Epeira diademata. The glands 
occupy the entire floor of the abdomen. They have been very 
thoroughly investigated by Apstein,' and may be divided into 
five kinds. 
On either side of the abdomen there are two large “ ampul- 
laceal” glands debouching on “ spigots,’ one on the anterior, and 
one on the middle spinneret ; there are three large “aggregate ” 
glands which all terminate on spigots on 
the posterior spinneret ; and three “ tubuli- 
form” glands, two of which have their 
orifices on the posterior, and one on the 
middle spinneret. Thus, in the entire 
abdomen there are sixteen large glands, 
terminating in the large fusulae known as 
spigots. In addition to this there are 
about 200 “ piriform” glands whose open- 
ings are on the short conical fusulae of 
the posterior and anterior spinnerets, and =a 
about 400 “aciniform” glands which Fic. 187.—Spinning glands. 
debouch, by cylindrical fusulae, on the relate ais ae, 
middle and posterior spinnerets. Thus 
there are, in all, about 600 glands with their separate fusulae 
in the case of Epeira diademata. 
The great number of orifices from which silk may be emitted 
has given rise to the widespread belief that, fine as the Spider's 
line is, it is woven of hundreds of strands. This is an entire 
misconception, as we shall have occasion to show when we deal 
with the various spinning operations. 
A few families are, as has already been stated, characterised 
by the possession of an extra spinning organ, the cribellum, and 
1 Arch. f. Naturg. 55 Jahrg., i., 1889, p. 29. 
