LOLIGO PEALII LESUEUR 241 



pass obliquely backward to the upper surface giving off branches 

 to the rear half of the mantle and to the fins. The blood from 

 the median mantle artery passes through capillaries into the 

 mantle veins; that from the lateral mantle arteries into the 

 posterior venae cavas. The genital artery arises from the middle 

 of the ventral surface of the heart. Its blood passes through 

 capillaries into the genital vein. 



The system of veins is characterized by the considerable size 

 of the vessels and by their special relation to the excretory sys- 

 tem. The anterior vena cava the branches of which collect the 

 blood from the head is a vessel of considerable size running in 

 the median line below the liver toward the nephridial sac. On 

 entering the latter, it splits into a right and left arm which trav- 

 erse the nephridial sac and open into the respective branchial 

 hearts. The two arms have been called by Brooks the glandular 

 portion of the anterior vena cava because they are surrounded 

 by the urinary gland. Williams calls them the nephridial sinus 

 because of their wide lumen. The latter term is scarcely more 

 fortunate than the former, since in other cephalopods the two 

 arms are in no wise conspicuously enlarged. They may be 

 best designated as the nephridial arms of the anterior vena cava. 

 Into the right nephridial arm open the right pallial or mantle vein, 

 the right vena cava posterior, and the genital vein; into the left 

 the left pallial vein and the left vena cava posterior. The pallial 

 veins collect the blood from the forward portion of the mantle^ 

 blood that was carried there by the median mantle artery. The 

 pallial veins open into the nephridial arms of the anterior vena 

 cava close to the branchial hearts. The right and left posterior 

 venae cavae are large vessels collecting the blood from the rear 

 half of the mantle. On entering the nephridial sac, each vein 

 forms a slightly dilated nephridial portion of the (right or left} 

 posterior vena cava (Brooks calls this portion the glandular 

 portion of the posterior vena cava, while Williams considers 

 it to be a part of the nephridial sinus). The nephridial portion 

 is surrounded by the end of the urinary gland. Between the 



