166 ARACHNIDES. 



diastole of the heart. Both sexes frequently eject from the 

 anus an excrementitious fluid, part of which is milk-white, and 

 the remainder black as ink. 



The nervous system is composed of a double cord occupy- 

 ing the median line of the body, and of ganglions which dis- 

 tribute nerves to the various organs. M. Dufour has not been 

 able to determine tlie number and disposition of these gang- 

 lions, 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 v.ant of those relative to the organ of the circulation 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, ex- 

 hibits depressed points varying both in number and arrange- 

 ment. 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 exter- 

 nally 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 with 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 wiiose number exactly 

 equals that of the pulmonary sacs. When there are four, a 

 sort of fold or annular vestige found even in those where there 

 are but two, and placed directly 'behind them, forms a line 

 that separates the two pairs. 



The females have two very distinct ovaries, lodged in a spe- 

 cies of capsule formed by the liver. In an unfecundated state 

 they appear to be composed of a spongy, flaky kind of tissue, 

 formed by the agglomeration of rounded, and scarcely visible 

 corpuscles, which are the germs of eggs. As the results of 



