204 



PHYSIOLOGY OF THE INVERTEBRATA. 



close to the pulmonary sac. It consists of an auricle and 

 a ventricle. The aorta proceeds from the ventricle, and 

 divides into two branches : one of these passes forward and 

 ramifies in the head and foot, while the other passes back- 

 wards and dorsally to the viscera, where it also ramifies. 

 The arterial branches terminate by opening into lacunje ; 

 from these the blood passes through the pulmonary arteries 

 to the lung, and thence through the pulmonary veins, which 

 ultimately join to form a large pulmonary vein which leads 

 into the auricle. The organ of Bojanus, or kidney, " lies 

 close to the pulmonary sac in the course of the current of the 

 returning blood." 



Antr. vena > 

 cava. 



Xephridium 

 (kidney). 



Ventricle. 

 Vein. •^^ 



Antr. aorta. 



Efferent 

 branchial 

 vessels. 



Gill. 



Afferent 

 branchial 



vessels. 



Auricle. 



:^ Post, vena 

 cava. 



Capillaries. Post, aorta. 



Fig. 46.— Blood Systkm and Nephkidia of Skpia. 



(3) The Cephalopoda.— "^hQ circulatory system of Sepia is 

 seen in Fig. 46. " The heart is placed upon the posterior face 

 of the body, on the haemal side of the intestine, and receives 

 the blood by branchio-cardiac vessels, which correspond in 

 number with the gills ; and, as they are contractile, might be 

 regarded as auricles. The gills themselves have no cilia, and 



