82 



ZOOLOGY. 



for the ingress of the venous blood. The colorless blood 

 is pumped by the heart backwards and forwards through 

 three anterior arteries, one median and two lateral, the 

 median artery passing towards the head over the large 

 stomach, and the two lateral, or hepatic arteries, passing 

 to the liver and stomach. From the posterior angle of the 

 heart arise two arteries; the upper, a large median artery 

 (the superior abdominal), passes along the back to the erd 

 of the abdomen, sending off at intervals pairs of sm-11 

 arteries to the large masses of muscles filling the abdomi- 

 nal cavity; the lower is the second or sternal artery, which 

 connects with one extending along the floor of the body 

 near the thoracic ganglia of the nervous cord. There are 

 no veins such as are present in the Vertebrates, but a series 

 of venous channels or sinuses, through which the blood re- 

 turns to the heart. There is, however, a large vein in the 

 middle of the ventral side of the body. 



The blood is driven by the heart through the arteries, and 



flab 



-rrv 



J-V 1 end. 

 Fig. 97. — C, first maxillipede of lobster. 



a large part of it, forced into the capillaries, is collected by 

 the ventral venous sinus, and thence passing through the 

 gills (Fig. 97, gill, where it is oxygenated, returning to 

 the heart. 



The gills are appendages of the three pairs of maxilli- 

 pedes and the five pairs of feet, and are contained in a 

 chamber formed by the carapace; the sea- water passing into 

 the cavity between the body and the free edge of the cara- 



