744 



ZOOLOGY 



SECT. 



Immediately below the thin integument of the anterior wall of 

 the mantle-cavity lies a characteristic organ the ink-sac (Fig. 

 667, ink. s. ; Fig. 670, i.). This is a pear-shaped body, a portion of 

 the interior of which is glandular and secretes a black substance 

 the ink or sepia which collects in the main cavity of the sac and 

 is discharged by a cylindrical duct opening into the rectum close to 

 the anal aperture. When the Cuttle-fish is startled it discharges 

 the ink, which, mixing with the water in the mantle-cavity, is 



ejected through the funnel as a black 

 cloud, under cover of which the 

 animal may escape from a threatened 

 a u uaciv . 



E 



FIG. 60S. Sepia officinalis, jaws. FIG. 669. Sepia, median section through the buccal 

 A, in situ ; B, removed and slightly mass. ft. buc. buccal ganglia ; g. stom. stomato- 

 enlarged. (From the Cambridyc gastric ganglia ; </ust. supposed gustatory organ ; 

 Natural History.) jaivl, posterior jaw ; jawl, anterior jaw ; oe. oeso- 



phagus ; prrist. circular lip ; rad. radula. (After 

 Keferstein.) 



Vascular System. The heart (Figs. 671, 672, and 674) of the 

 Cuttle-fish consists of a ventricle and two auricles. The ventricle 

 (vent.}, which is divided into two lobes by a constriction, is somewhat 

 obliquely placed, but the rest of the vascular system is almost 

 completely equilateral. At its oral end the ventricle gives off 

 a large vessel the oral aorta (aorl.) ; aborally it gives origin 

 to a much smaller dboral aorta (aort'), which bends over tin- 

 ink-sac and supplies the aboral portions of the body. The arteries 

 which lead off from the aortse communicate by their ultimate 

 branches with a system of capillaries, and these with a system 



