$ 315. THE ARACHNOIDAE. 889 
canals, which are interlaced in a screw-like manner, and open at the six 
spinnerets ;® 2. Six long, flexuous tubes, which gradually enlarge into as 
many pouches, and are then continuous, each, into an equally long excre- 
tory duct which forms a double loop; 3. Three pairs of glandular tubes 
similar to the preceding, but which open externally through short excre- 
tory ducts; 4. Two groups of multiramose follicles, whose pretty long 
excretory ducts run to the two upper spinnerets ; 5. Two slightly ramified 
caeca, varicose at intervals, and which terminate, by two short excretory 
ducts, in the middle spinnerets. 
Most Araneae have three pairs of spinnerets, that is, papillae in the 
form of an obtuse cone; the middle pair of these is composed of two, and 
the anterior and posterior pairs, of three articles, The apex of these 
papillae defines the passage of the thread, and is surrounded by stiff 
bristles and hairs, and dotted with numerous small, horny tubes, which are 
only prolongations of the excretory ducts. Each of these tubes is com- 
posed of two pieces; one, basilar and thick, the other, terminal and very 
small, and through the orifice of which the web-liquid escapes in the form 
of a very delicate thread.” The number of these tubes varies according 
to the species, the age, and the sex.“ Those belonging to the unbranched 
glands are distinguished from the others by their size. With some species 
of Clubiona and Drassus, there are, beside the usual six spinnerets, two 
others, composed of a single article and joined together. This fourth pair 
is situated on the belly, forward’ of the others, and is connected with a 
kind of comb (Calamistrum) attached to the metatarsus of the two poste- 
rior legs. 
With Phalangium, there is an S-shaped glandular tube situated on the 
digestive canal, and ending at both extremities by a narrow duct. Its 
nature is yet unknown; and although the outlet of these excretory ducts 
has not been discovered, yet as this apparatus is found only with males, it 
may well be supposed to have some connection with the genital functions. 
‘With some Acarina, there are certain phenomena indicating that these 
animals have special secretory organs, whose product, like the web-liquid, 
is hardened on its evacuation. Thus, with some species of the genus 
Uropoda, there is formed, by a substance of this kind, a peduncle situated 
at the posterior part of the abdomen, and by which these animals fix them- 
selves to insects. This stalk, dilated disc-like, was taken formerly for an 
organ of suction.“ Many species of Hydrachna fix, by a kind of glue, 
8 Mygale has only this one kind of glands ; they 
form four groups, situated immediately at the base 
of the spinnerets. 
9 The spinnerets and terminal tubes have al- 
ready been very exactly figured by Leewwenhoek 
(oc. cit. p. 326, fig. 5, 6), and by Roesed (loc. cit. 
Taf. XXXVIIL. fig. 4). See also Lyonet, loc. cit. 
p. 387, Pl. XIX. fig. 6-12 ; Wasmann, loc. cit. p. 
20, fig. 31-34, and H. Meckel, loc. cit. p. 54, Taf. 
III. fig. 43-45. 
10 There are more than a thousand of these 
tubes on the spinnerets of Epeira ; with Tegena- 
ria, there are about four hundred ; with Clubiona 
and Lycosa, three hundred ; with Segestria, one 
hundred, and their number is even less with the 
small spiders; see Blackwell, Tr: t. of the 
Linn. Soc. XVIII. 1841, p. 219, and Ann. of Nat, 
Hist. XV. p. 221, and Menge, loc. cit. p. 24. 
li This pair of accessory spinnerets is found, ac- 
33%* 
cording to Blackwell (loc. cit.), with Clubiona 
atrox, Drassus viridis: imus, parculus and ¢xi- 
guus. 
12 See Treviranus, Verm. Schrift. I. p. 37, Taf. 
Il. fig. 17, h., and Tulk, loc. cit. p. 252, Pl. IV. 
fig: 21. 
13 See Degeer, loc. cit. p. 52, Taf. VII. fig. 16, 
and Duges, Ann. d. Sc. Nat. II. p. 30 (Uropoda 
vegetans). The peduncle is more or less long and 
often attached to the hardest parts of the Coleop- 
tera. Its formation is connected with some meta- 
morphosis of these animals, and is without doubt 
due to a secretion produced by some glandular ap 
paratus opening near the anus. This view ap- 
pears, at least, more natural than that advanced 
by Duges (loc. cit. p. 30), and adopted by Dujar- 
din (Compt. rend. loc. cit. p. 1160), that this pe- 
duncle is formed by the feces hardening after their 
escape from the anus. 
