EXPLANATION OF THE TLATES. 



To avoid useless repetitions in the description of the Figures, the same letters are used, throughout the** Plati^ 

 [I. -VIII.], to denote identical parts. It will greatl}- facilitate the readiug of this memoir to become familiar with 

 the notation here adopted. 



Explanation of the Lettering on Plates I. -VIII. 



a, anus. 



b, dorsal or water pore, madreporic opening. 



c, alimentary canal. 



d, digestive cavity, stomach. 



d', abactinal water-tubes in angle of rays of young 

 Starfish. 



d", water-tubes of lateral line of rays of young Star- 

 fish. 



d'", water-tubes of median line of rays of young Star- 

 fish. 



e, eye of Starfish at base of odd tentacle {t'). 

 e', median anal arms of Brachiolaria. 



e", dorsal anal arms of Brachiolaria. 

 e'", ventral anal arms of Brachiolaria. 

 e"", dorsal oral arms of Brachiolaria. 

 e^, ventral oral arms of Brachiolaria. 

 e®, odd terminal oral arm of Brachiolaria. 



f, brachiolar arms. 



f, branch of water-tube (w tv') leading into^! 



f", odd brachiolar arms. 



/'", surface- warts at base of odd brachiolar arm {/")■ 



h, hole of cul de sac of water-tube w. 



I, central abactinal plate of young Starfish. 



/j, Zj, /j, . . interbrachial abactinal plates of young 



Starfish. 

 2, /j) ^2' • • brachial plates of young Starfish. 

 m, mouth. 



rn', pistol-shaped oral pouch of oesophagus. 

 m", anal pouch of oesophagus, 

 n, opening for passage of ambulacral sucker. 

 0, cESophagus. 



p, spines on edge of ray of Starfish. 

 p^, spines of exterior rows along abactinal surface of 



rays. 

 p<^, spines of middle row on abactinal surface of rays. 

 Pg, central spine of abactinal surface of Starfish, on 



central plate (/j). 



p~, plate at junction of adjacent rays (oyarian plate). 



p', p", different forms of pedicellariae. 



r, abactinal surface. 



r', first set of five limestone rods which appear on 



abactinal surface, and which eventually become 



tlie brachial plates (/j)- 

 r", second set of five interbrachial limestone rods, 



which eventually become the interbrachial plates 



r''i-]-"i rays of young Starfish; r'l' being ray next 

 to madreporic body, when Brachiolaria is seen 

 from the dorsal side. 



s t and s, actinal region. 



t, t, t, . . tentacles of the young Starfish. 



t', odd tentacle. 



<", ambulacral tube. 



«, lateral ambulacral plates, surmounted by spine. 



w', median ambulacral plates with very small spines. 



V, vibratile chonl, anal part. 



v', vibratile chord, oral part. 



w, water-tube, developing abactinal area, 



ic', water-tube of Brachiolaria leading to madreporic 

 opening (h), developing actinal area. 



w tc', portion of water-tube of B .ichiolaria formed by 

 junction of w and tc'. 



In all the figures of the Brachiolaria (Plates I. -IV.), 

 the attitude which has been given to thorn is not 

 a natural attitude. Tliis has been <lone pur- 

 posely, for the sake of making the comparison 

 with the memoirs of Miillcr easier. The only 

 figure of a Brachiolaria which is in its n .tural 

 attitude is that of PI. VIII. Fig. 8. The young 

 Brachioluia does not, however, move with the 

 anal part below, till the latter is loaded down by 

 the development of the Starfish, and we see 

 them swimmincc aboui, l)efore that time, almost 

 in every possible attitude. 



