154 



LOWKI! INVEirrEIUlA TES. 



nuliiiu'iilan-. Into the intestiiie djteiis a duct which divides in two main branches. These 

 branches subdivide into numerous follicles, tile whole formiiio- what is supposed to be the 

 liver, since it contains a bitter flvud like bile. The nervous system consists of a nerve 

 which runs, as a longitudinal ridue, along each ambulaeral groove, and of a ring aroun<l 

 the mouth. At the end of each arin a rudimentary eye, continuous with the ambidaeral 

 nerve, is placed at the end of a nmditied tentMcle. The water system consists of a 

 canal running the entire length of each arm. This canal is jilaced in the angle formed 

 by the ambulaeral plates, and is thus extern.al to them. It is separated by a strong 

 ]iartition from a second canal which intervenes between it and the nervous Ijand which 

 forms tile liottoiu of the ;nnl)ulacral uroove in the livint;- animal. This lower canal, 



KiG. 13.").— Bipimiai-ia of star-flsli : am 

 ambulacra ; i, intestine; o, anus; «', 

 stomach; v, water tubes. 



rudimentary 

 esophagus; s, 



Fig. 136. — Late 



which is itself divided into two luilves, is c;illed the :iiiibul;icral neur;il c;ui;d, ;md com- 

 municates with a cireulai- canal around the mouth. Fi-oni ojiposite sides of the 

 amlinlacral canal of the water system, short branches j)ass up lietween the ambulaeral 

 ossicles to the ampulla^, which are s;ics with muscular walls lying above the ambulaeral 

 plate.s, and within the cavity of the arm. Eadi ampulla communicates with a ]>edicel 

 or sucker by the ])ores in the ambulaeral ])lates, as liefore described. The cavity of the 

 body ;ind rays is filled with a watery fluid containing corjiu.seles, evidently represent- 

 ing the blood of higher animals. Pores, by^ which water can enter the liody cavity, 

 are often present upon the aboral as])eet of a star-fish. 



The se.xes are distinct, but can only be distinguished by a microscopic e.xamination 

 of the ghmds, which are situated on each side of the interior of the arms, or at the 

 junction of the body with the r;iys. As the jjlates which enclose the base of the arms 



