38o 



MOLLUSC A. 



Its two ducts conduct the digestive juice to the region where 

 stomach, "pyloric sac," and intestine meet, and these ducts 

 are fringed by numerous vascular and glandular appendages 

 which are called " pancreatic," though in reality formed as 

 an outgrowth of the nephridia. Far forward, in front of the 

 large digestive gland, lie two small white glands on each side 

 of the gullet. Their ducts 

 open into the mouth, and 

 their secretion contains a dias- 

 tatic ferment. At the other 

 end of the food canal, the ink 

 sac full of black pigment, pro- 

 bably of the nature of waste 

 products, opens into the rec- 

 tum close to the anus. This 

 ink sac may be called a much 

 enlarged anal gland, for while 

 most of the bag is made of 

 connective tissue and some 

 muscle fibres, a distinct gland 

 is constricted oif at the closed 

 end, and the neck is also 

 glandular. 



Fig. 121. — Diagram of the 

 structure of Sepia. (Mainly 

 after Pelseneer.) 



a., Eight short arms around mouth ; 

 l.a.^ one of the two long arms ; b., beak 

 of the mouth ; e.g., cerebral ganglia 

 with commissures lo the others; R., 

 ^ye ; £., gullet ; d.g., digestive gland ; 

 St., stomach; a.., anus; sh., shell sac 

 with sepiostaire ; k., kidney; R., 

 Reproductive organ; br.h., branchial 

 heart; g., a gill; i.b., ink bag; in.c, 

 mantle cavity ; /., funnel. 



Vascular System. 

 The blood of Sepia is 

 bluish, owing to the presence 

 of hsmocyanin in the serum ; 

 the blood cells are colourless 

 and amoeboid. The median 

 but somewhat oblique ven- 

 tricle of the heart drives the 

 blood forward and backward to all parts of the body. 

 It reaches the tissues by capillaries, and apparently also 

 by lacunar spaces. The venous blood of the head region 

 is collected in an annular sinus round the basis of the 

 arms, and passes towards the heart by a large vena cava 

 which divides into two branchial veins, covered by spongy 

 outgrowths of the nephridia. Joined by other vessels 

 from the apical region of the viscera, each branchial vein 

 enters a " branchial heart " at the base of each gill. The 



