56 



Z00L0O7. 



each s;^c is bouud down by two letifictor muscles attached to the 

 median ridge Ij'iiig between the two rows of water-sacs (ampullit, see 

 also Fig. 61). The stomach ends in a short intesline, the limits be- 

 tween the two nut distinctly seen. The intestine suddenly contracts 

 and ends in a minute rectum situated in an angle between two of 

 flv:^ fleshy ridges radiating from the centre of the disk. Appended 

 to the intestine are the " cceca " or "liver" (Fig. 60, b), consisting of 

 two long, tree like masses formed of dense branches of from four to 

 six pear-shaped follicles, connecting by a short duct with the main 



Fig. 61.— Diag^ram of the water-system of a star-fish, a, madreporic body; b, 

 stone-canal; c, circumoral water-tube; d, radial water-tubes; e, ampuUas; /, 

 feet or ambulacra. After Brooks. 



stem. The two main ducts unite to form a short common opening 

 into the intestine. The cajca are usually dark, livid green, and 

 BBcrete a bitter digestive fluid, representing probably the bile of the 

 higher animals. 



The ovaries (Fig. 60, o) are long racemose bodies lying along each 

 side of the interior of the arms, and the eggs are said to pass ont by 

 short narrow oviduct (nv) through an opening between two plates on 

 each side of the base of the arms, the opening being small and difli- 

 cult to detect. 



The water- vascular system consists of the madreporic body, the 

 "stone-canal " (Fig. 60, 0, the ring or circumoral canal (w), and the ra- 



