in the Spiders of the, Genus hycosa. 23 



too delicate and too pellucid to be dissected, curve downwards 

 and forwards towards the lungs; they become enlarged and 

 apparently confounded together in proportion as they approach 

 the latter, so as to constitute a lacuna parallel to the large lon- 

 gitudinal muscles which occupy the lower region of the abdomen. 

 This space is transparent and filled with fluid in Pholcus'^^. 

 This description is in perfect accordance with what we have said 

 of the LycoscBy except as regards "the innumerable vessels/^ 

 Duges, however, does not appear to have seen the blood in 

 circulation. 



There was a time when M. Blanchard did not go so far as 

 Duges in the multiplication of the blood-vessels in the Arach- 

 nida. He said, at this period f^ " What appears to be remark- 

 able in the vascular system of Epe'ira is the small number of 

 ramifications presented by the arteries ; for my investigations 

 and experiments have been repeated upon a very large number 

 of individuals, and always with success ; I think, therefore, that 

 few details can have escaped me.^^ The opinions of the learned 

 anatomist have become greatly modified since that time. At any 

 rate, M. Blanchard then represented, in Epe'ira diadema, two 

 vessels nearly in the position of the longitudinal sinuses which 

 we have described; but he regarded them as pneumocardiac 

 vessels destined to convey the oxygenated blood to the posterior 

 part of the heart. He therefore assumed that the movement of 

 the blood took place in these vessels in a direction precisely 

 opposite to the real direction of this movement. Far be it from 

 me to reproach him for having been mistaken on this point; 

 for the method of injections alone could never solve the question 

 of the direction of the movement. 



Hitherto I have only considered the abdominal circulation ; 

 but I shall now speak of that of the cephalothorax. The arterial 

 portion of this circulation is now well known, thanks to the 

 investigations of Duges, and especially of M. Blanchard. The 

 ramifications of the aorta in the Lycosa saccata are nearly iden- 

 tical with those figured by M. Blanchard in Mygale avicularia. 

 This large vessel traverses the abdominal peduncle above the 

 digestive canal, follows an ascending direction beneath the pos- 

 terior dorsal region of the cephalothorax, and penetrates the 

 stomach-ring. At this point it divides into two secondary aortas, 

 which soon curve downwards so as to form a crook. Imme- 

 diately beyond the crook, each secondary aorta spreads out like 

 a duck's foot, and gives origin to several branches. These are, 

 first, the ophthalmic artery, then the four pedal arteries, the 

 artery of the deutognath, and that of the protognath. Each of 



* This remark with regard to the Pholci is perfectly correct. 

 t Ann. Sc. Nat. 3« ser. 1849, tome xii. p. 324. 



