§ 315. THE ARACHNOIDAE. 389 



canals, which are interlaced in a screw-like manner, and open at the six 

 spinnerets j'*^' 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 discovei*ed, 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 Jlfy^a/e has only this one kind of glands ; they cording to Blackwell (loc. cit.), with Clubiona 



form four groups, situated immediately at the base atrox, Drassus viridisrimus-, parculus and exi- 



of the spinnerets. guus. 



y The spinnerets and terminal tubes have al- 12 See Treviranus, Verm. Schrift. I. p. 37, Taf. 



ready been very exactly figured by Leeuwenhoek III. fig. 17, h., and Tulk, loc. cit. p. 252, PI. IV. 



(loc. cit. p. 326, fig. 5, 6), and by Roesel (loc. cit. fig: 21. 



Taf. XXXVIII. fig. 4). See also Lyonet, loc. cit. 13 See Dei^eer, loc. cit. p. 52, Taf. VII. fig. 16, 



p. 387, PI. XIX. fig. 6-12 ; Wasmann, loc. cit. p. and Dugeii:, Ann. d. Sc. Nat. II. p. 30 (^Uropoda 



20, fig. 31-34, and H. Meckel, loc. cit. p. 54, Taf. vegetans). The peduncle is more or less long and 



III. fig. 43-45. often attached to the hardest parts of the Coleop- 



10 There are more than a thousand of these tera. Its formation is connected with some meta- 



tubes on the spinnerets of Epeira ; with Tegena- morphosis of these animals, and is without doubt 



ria, there are about four hundred ; with Clubiona due to a secretion produced by some glandular ap 



and Lijcosa, three hundred ; with Scgestria, one paratus opening near the anus. This view ap- 



hundred, and tlieir number is even less with the pears, at least, more natural than that advanced 



small spiders ; sec Blackwell, Transact, of the by Dugis (loc. cit. p. 30), and a<lopted by Dujar- 



Linn. Soc. XVIII. 1S41, p. 219, and Ann. of Nat. din (Compt. rend. loc. cit. p. 1160), that this pe- 



Hist. XV. p. 221, and Mcnge, loc. cit. p. 24. duncle is formed by the feces hardening after their 



U This pail' of accessory spiimerets is found, ac- escajie from the arms. 



33* 



