"§> 312. THE ARACHNOIDAE. 385 



ramify through the whole body like those of insects, there are three pairs 

 of stigmata/'" With the Phalangidae, the trachean system is highly 

 developed, arising from two stigmata concealed under the coxae of the 

 posterior legs, each of which has a horny valve. The two large trunks 

 given off from these stigmata, run obliquely to the cephalic extremity ; they 

 intercommunicate by a transverse anastomosis, and give oif, in all direc- 

 tions, numerous branches which are spread over the abdominal viscera, and 

 penetrate even the palpi and legs.*^* 



With many of the Araneae, there are, on the under surface of the abdo- 

 men, two orifices which lead into two pulmonary sacs, beside two other 

 openings belonging to the trachean system. With Scgestria, Dysdera,'^^ 

 and Argyroneta,'''' there arise from these two stigmata two large trunks 

 surrounded by a kind of horny trellis-work. From the extremity of these 

 trunks are given off innumerable, very small tracheae, which are un- 

 branched and without the spiral filament. They are disposed in tufts, and 

 are distributed, some in the abdomen, and others in the cephalothorax, 

 penetrating even to the extremity of its members. With Salticus, and 

 Micryphantes,^^^ the two stigmata are situated at the posterior extremity 

 of the body, far removed from the pulmonary sacs, and send oflF, directly, 

 two tufts of unbranched tracheae, which are distributed exclusively to the 

 abdominal viscera.'^' There is, with the other Araneae, a trachean 

 system, very imperfect it is true, which has hitherto been overlooked by 

 anatomists. Directly in front of the spinnerets, there is, with most species, 

 a transverse fissure difficult to be seen, which leads into a very short 

 trachean trunk. From this trunk are given off four simple tracheae 

 which, singularly, are not cylindrical, but are flattened, riband-like, and 

 without a trace of a spiral filament ; these extend, with a gradual attenua- 

 tion, to the base of the abdomen. These riband-like, silvery tracheae are 

 composed of a thin, but solid, homogeneous membrane, which is enveloped 

 by a soft, ti'ansparent pellicle corresponding to a peritoneum. The air 

 received into these organs is separated into as fine portions as that of the 

 lungs. These tracheae differ therefore, prominently, from those of the 

 other Arachnoidae.*^*^^ 



ignorant of their existence, and even lately, that finely divided, while that in the cylindrical tra- 



Tulk (Annals of Nat. Hist. XV. p. 57) should cheae given off from these trunks, forms a continu- 



have failed to see them with Obisium. ous column. 



i See Muller, Isis, 1828, p. 711, and Milne Ed- 10 I have found this trachean system with 



wardu^ R^gne anim. lUustr. Arachuides, PI. II. Epeira, Tetragnatkus, Drasstis, C/ubiona, 



5 Treviranus, Verm. Schrift. I. p. 32, Taf. IV. Theridion, Lycosa, Diomedes and several 



fig. 19, and Tulk, loc. cit. p. 327, PI. V. fig. 33. others. I have been unable to perceive it in 



^ Duges, in "Le Temps," 1835, No. 1942, individuals escaping from the egg. Tliomisus 



Peuilleton, Acad. d. Sc. Seance du 9 Fevrier, or viaticus is the only species in which the four 



Froriep\i neue Notiz. XLIII. p. 231, or Ann. d. flattened trachean trunks iire ramified, and thus 



Sc. Nat. VI. p. 183, an<i R^gne animal, Arach- serves as the passage to the most hiirlily developed 



nl<ks, PI. III. fig. 4, V. fig. 4. See also Owen, trachean system of Saltictia. By direct light. 



Lectures, &c., p. 259, fig. 112. they appear black, and thus it is possible tliat they 



" Grube, loc. cit. p. 300, and Menge, loc. cit. p. may have sometimes been taken for urinary canals. 



22, Taf. I. fig. 6-14. But this error is unnecessary, for these last vessels 



'i Menge, loc. cit. p. 23, Taf. I. fig. 15. burst from the slightest pressure and effuse granu- 



9 I have had an opportunity to satisfy myself of lar contents, while the tracheae under such treat- 



the existence of this interesting trachean system ment become transparent, their contained air 



vith Segestria, Argyroneta, Salticus-i and Micry- making its escape, and when the pressure is with- 



pkantes. I should also add that the principal drawn they resume their black color.* 

 Trunks are flattened, and that the contained air is 



, [ 5 312. note 10.] See also for these anomalous elongated pulmonary sacs ; but especially Leuc- 



traclicae, lilanchard (loc. cit. Ann. d. Sc. Nat. A-nrt (Ueber denBau und die liendeutung der sog. 



.\.II. 1S49, p. 345), who regards them as only Lungen bei den Arachniden, in StcftoW and' iCoZ/i- 



33 



