204 P'HYSIOLOGY 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 lacunas; 

 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. 



Nephridium 

 (kidney). 



Post, vena 

 cava. 



Capillaries. TPost. aorta. 



Fig. 46. — Blood System and Nephridia of Sepia. 



(3) The Ceplictlopoda. — The circulatory system of Sepia is 

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

 of the body, on the hsemal 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 



