ANATOMY OF THE KINGt-ORAB. 299 



The heart is tubular, with eight pairs of valvular openings 

 for the return of the venous blood which flows into the 

 pericardial sac from all parts of the body ; the arterial blood 



Fig. 265.— Nervous and part of the circulatory system of Limulus polypTiemus, the 

 King-Crab. a, vent ; «, cesophagua ; &, bi ain ; o, nerve to the smaller eyes ; &, nerve 

 to the larger eyes ; s. nervc-ring around the oesophagus. All the nerves are surround- 

 ed by an arterial coat. — After Milne Edwards. 



is sent out from the arteries branching from the front end 

 of the heart flowing around the upper side of the edge of the 

 cephalo-thorax through numerous minute vessels. Also there 

 are a pair of branchial arteries, and two arteries in the base of 

 the spine. 



