VI 



ABACHNOIDEA—BLOOD-VASOULAB SYSTEM 



527 



cephaliea. It is perhaps the remains of an originally long tubular 

 heart which reached as far as the anterior region of the body, and 

 which ceased to develop ostia. 



The heart lies in all AFaehnoidea in the abdomen, or in that part 

 of the body which corresponds with the abdomen. 



Scorpionidee (Fig. 370, A). — The extended tubular heart of the Scorpion 

 lies in the pre-abdomen. It is 8 chambered, and has 8 pairs of lateral openings. 

 From the posterior end of each chamber a pair of lateral arteries diverges. The heart 

 is continued posteriorly into an aorta of the post-abdomen, and anteriorly into an 



ac 



Pio. 370.— The hearts of various Araoh- 

 noidea. A, Scorpion (after Newport). B, 

 Araneid. C, Obisium silvatioum, juv. 

 (Pseudosemyionid) (after Wmkler). D, 

 Gamasus fucorum, larva (after Winkler). 

 E, Toiiog Phalangia. (after Winkler). 



cui 



Fig. syi.— Heart of a Spider (Plwlciis 

 phalangoides) (after Sohlmkswitsoll). ac, 

 Aorta cephaliea ; o, ostia of the heart ; vp, 

 origin of the vena pulmonalis ; f], ao. «3> 

 lateral arteries of the heart ; aa, aorta or 

 arteria ahdominalis ; m, alary muscles, 

 attached to the pericardium ; pc, pericardium. 



aorta cephaliea which runs through the cephalo-thorax. From the posterior aorta 

 several lateral pairs of arteries arise. Immediately in front of the most anterior pair 

 of ostia, and thus at the root of the aorta cephaliea, a lateral artery is likewise given 

 off on each side. A little further forward there are two more lateral arteries running 

 downwards, and embracing the resophagus, so forming an oesophageal ring. From this 

 (esophageal ring arises a medio-ventral longitudinal vessel running backwards ; this 

 lies above the ventral chord, and is called the supraneural vessel. In front of the 

 vessels forming the oesophageal ring the aorta cephaliea gives off numerous other 

 arteries, principally to the 6 pairs of extremities. 



All the arteries apparently open into a lacunar system of the body, through which 

 the blood flows in special currents, those of the pre-abdomen bathing the book -leaf 



