280 ARACHNIDES. 



several sacs, and then of a second stomach or dilatation sur- 

 rounded with silk. According to the observations of M. Leon Dufour 

 — Ann. des So. Phys.VI — it occupies the greater part of the abdomi- 

 nal cavity, and is immediately enveloped by the skin. It is of a 

 pulpy consistence, and is formed of granules*, whose individual ex- 

 cretory ducts unite in several hepatic canals, which pour the secreted 

 matter into the alimentary tube. In the middle of its superior sur- 

 face is a depressed line, where the heart is lodged, and which divides 

 that organ into two equal lobes. Its form, like thatof the abdomen, va- 

 ries according to the species ; thus in the Epeira sericea its contour is 

 festooned. In this subgenus, as in the Lycosa tarentula, its surface is 

 covered with a whitish coat split into areolae, which, in several species, 

 are easily perceived through the glabrous skin ; they may be seen 

 obeying the impulse communicated to them by the systole and diastole 

 of the heart. Both sexes frequently eject from the anus an excre- 

 mentitious fluid, part of which is milk-AVhite, and the remainder black 

 as ink. 



The nervous system is composed of a double cord occupying the 

 median line of the body, and of ganglions Avhich distribute nerves to 

 the various organs. M. Dufour has not been able to determine the 

 number and disposition of these ganglions, but from the figure of this 

 system given by Treviranus — Veber deninnern, bau des Arachniden, 

 tab. V. fig. 45 — there are but two. The observations of the latter 

 will also supply the want of those relative to the organ of the circu- 

 lation by M. Dufour, which, according to him, appears to consist of 

 a simple dorsal vessel, as well as with respect to the testes and 

 spermatic vessels, on which he is totally silent. 



The dorsal region of the abdomen in several Araneides, those 

 especially which are glabrous or but slightly pilose, exhibits depressed 

 points varying both in number and arrangement. M. Dufour has 

 ascertained that these little orbicular depressions are caused by the 

 insertion of filiform muscles, which traverse the liver, and which he 

 has also observed in the Scorpions, 



The one or two pairs of pulmonary sacs are indicated externally 

 by as many yellowish or whitish spots near the ventral base, and 

 immediately after the segment, which, by means of a fleshy thread, 

 unites the abdomen Avith the thorax. Each pulmonary bursa is formed 

 by the superposition of numerous, triangular, white, and extremely 

 thin leaflets, which become confluent round the stigmata, and Avhose 

 number exactly equals that of the pulmonary sacs. When there are 



* The liver of the Scorpions is composed of pyramidal and fasciculated lobules, a 

 circumstance which seems to announce a more advanced degree of organization. 



