CEPHALOPODA 



517 



anterior end of the visceral hump is seen the central anus at the end 

 of a long papilla, the shorter renal papillae immediately on each side, 

 and on the left side only Xh.^ genital aperture, also at the end of a long 

 papilla. More posterior still are the large and typical ctenidia. 



On the face of the visceral hump in mature animals the accessory 

 genital glands are seen through the skin ; the chief of these are the 



-abd.v. 



Fig. 379. Sepia offici?ialis. Dissection from the ventral side to show kidneys 

 and blood vessels. Arrowsshowthedirectionof flow of blood, abd. z;. abdominal 

 vein; a.ao. anterior aorta; au. auricle; a_ff.v. afferent branchial vein; br.ht. 

 branchial heart; eff.v. efferent branchial vein; k.d. opening into dorsal sac of 

 kidney (see arrow); k.t. excretory tissue surrounding the vena cava; pal.v. 

 pallial vein; p.ao. posterior aorta; r.p.a. opening into kidney cavity of the 

 renopericardial canal, r.p.c; st.g. stellate ganglion; ven. ventricle; v.cav. 

 vena cava. Other letters as in Figs. 377, 378. Original. 



nidamental glands of the female which occupy a considerable area. 

 Between these and in front of them is the accessory nidamental gland. 

 Posterior to them is the ink sac, usually seen through the integument 

 from which a narrow duct runs ventral to the rectum, opening into it 

 a short distance behind the anus. The first step in dissection is to strip 

 off the skin and then dissect out the gland and its duct as carefully 

 as possible. It usually contains a large amount of the ink, which is 

 composed of granules of melanin pigment formed by the oxidation of 



