SEA-FISHERIES LABORATORY. 409 



pedes {art. 3, art. 4) are not symmetrical. The origin of 

 the artery going to the first maxillipede of the right side 

 is posterior to that of the left. In the case of the second 

 maxillipede the origin of the artery on the right side is 

 anterior to that of the artery on the left. 



Just in front of the branches to the first maxillipede 

 the sternal artery bifurcates, each part passing forward 

 and uniting again behind the mouth, thus forming a ring. 

 From this ring arteries are given off to the mandibles and 

 the first and second maxillae {art. 1, art. 2). 



Inferior Abdominal artery (PL IX, fig. 52, ia.art.). 

 The posterior part of the broad sternal artery is continued 

 as a narrow vessel which runs backwards over the " sella 

 turcica " and down the abdomen beneath the nerve cord 

 and the hind-gut. It gives off a few small branches to the 

 hind-gut and to the flexor muscles of the abdomen. 



Blood Sinuses and Yeins. (PI. IX, figs. 54, 55, 56.) 



The blood returning from the various parts of the 

 body to the gills is not enclosed in definite vessels, but 

 flows through irregular spaces known as sinuses. Generally 

 speaking, all the main organs of the body, such as the 

 alimentary canal, digestive gland, reproductive organs, 

 muscles, &c, have blood sinuses in close contact with 

 them. 



Above the cardiac fore-gut there is a large sinus — 

 the Dorsal sinus — which is situated above the epigastric 

 lobe of the bladder. There is also a smaller sinus 

 between this lobe of the bladder and the fore-gut. These 

 two sinuses are connected in front. 



The dorsal sinus passes down the front of the fore-gut 

 and is connected ventrally with a sinus which passes 

 backward beneath the stomach. At the level of the 

 oesophagus this sinus divides into a right and left portion. 



