114 E. A. Andreics — Anatomy of the {Spider Crab. 



arise mimerous branches wliich suj)})ly the dermis, reprofluctive 

 organs, and the muscles of the stoniacli ami mandibles. P^roni the 

 lower edge of the anterior face of the heart there arise two he})atic 

 arteries, one between each antennary artery and the lateral side of 

 the heart. These arteries and their branches have a yellow color 

 which renders it easy to trace them. They descend into the mass of 

 tlie liver and give off" numerous branches, which ramify throughout 

 the entire liver and cover the intestine in the thoracic cavity with 

 numerous fine vessels. 



From the posterior angle of the lieart and a little to one side of the 

 central line, the sternal artery (?•", fig. !■), the largest of all, arises. 

 From near its origin, between the cavity of the heart and the valves 

 of the sternal artery preventing the blood from flowing back into the 

 heart, there arises the slender superior abdominal artery {r'"). The 

 sternal aitery passes downward and slightly forward, sometimes on 

 the right and sometimes on the left of the median line, till near the 

 apodemal processes, when it sends off" from its posterior side the 

 slender inferior abdominal artery (;■"", fig. 20), and passing between 

 the two nervous cords which enter the abdomen, it turns forward 

 parallel to and but little above the sternal surface of the body. 

 From the descending portion a few delicate branches pass into the 

 liver mass; and two long ones run forward under the floor of the 

 pei-icardium. This large horizontal part of the sternal artery gives 

 off" six pairs of large branches (6-11, fig. 20), one to each segment 

 bearino" the ambulatory legs, and one to that bearing the thii-d max- 

 iliiped. As the artery closely follows the sternal surface it rises 

 with the cephalic flexure, and from this inclined portion gives off 

 two pairs of smaller branches, the posterior (5, fig. 20) supplying 

 the second maxillipeds, the anterior (3, 4, fig. 20) forking and sup- 

 ijlyino; the first maxillipeds and the second maxilhe. Behind the 

 moTith the artery forks, and each part giving off a branch to the first 

 maxilla (2), goes forward around the cesophagus, giving off a 

 branch into the mandible (1) and others to the muscles of the (i>so])h- 

 ao-us and forward over the endostoma. The six pairs of branches 

 iriven ofl" from tlie horizontal path of the sternal artery continue out 

 throut^h the apodemal cells into the appendages of the six posterior 

 thoracic segments, but each gives off besides numerous small branches 

 a laro-e branch (7'-ll', fig. 20) which subdivides and supplies the 

 adductor and abductor in both cells of tlie same segments. The 

 small superior abdominal artery (r'", fig. 1), which arises on the inner 

 side of the sternal artery at its origin, continues back close to the 



