ANIMALIA ARTICULATA. 



117 



external air by fissures or apertures called stigmata or spira- 

 cula ; there are from two to eight of them. Blood white ; 

 circulation in accordance with the mode of respiration. The 

 most of them feed on Insects; either seizing them in the 

 silky web which it fabricates, or catching them by running, 

 or leaping upon them when they approach too near their 

 retreat. Others live as Parasites, upon Vertebrated Animals ; 

 a certain species are found only in flour, upon cheese, and 

 different vegetables. 



ORDER I. PULMONARIA. 



Respiration by pulmonary sacs placed under the abdomen, 

 and communicating with the exterior air by spiracula ; some- 

 times there are eight, four on each side, sometimes four, or 

 two ; from six to eight smooth eyes ; heart consisting of a 

 large cylindrical vessel, sending the blood through the arte- 

 ries to the different parts of the body, and receiving by 

 the veins that which has traversed the respiratory organs. 

 Always four pairs of feet. Two remarkable families. 



Explanation of Fig. B, PL 33. Circulation of Pulmonaria : 

 1, the heart; 2, artery carrying blood to the head; 3, respi- 

 ratory apparatus ; 4, vessels which reconvey the blood from 

 the pulmonary sacs to the heart. 



FAMILY I. ARANEIDES. 



Foot-palpi without forceps at the end, and terminated at 

 most by one small hook ; four, or two, pulmonary pouches ; 

 last articulation of the chelicerse pierced near its extremity, 

 for the issue of a poison, proceeding from a gland placed in 

 the preceding joint. Abdomen soft, and furnished, in all, 

 with four or six nipples, fleshy at the end, cylindrical or 

 conical, articulated, situated very close to each other, and 

 pierced at the extremity with an infinity of little holes, for 

 the passage of a silky thread, issuing from reservoirs within. 

 Legs composed of seven articulations, of which the two first 

 form the hip, the next the thigh, the fourth and the fifth the 

 tibia, and the two others the tarsus terminated by two or 



