MEM. M. C. Z., IX. No. 2.— ECHINODERMATA. 27 



22. Odd terminal tentacle, with tlie eye-speck (f) of a young Asteracanthion about in the stage of fig. 18. 



23. Shows the process of resorption of the Brachiolaria into the young Starfish ; it coniniences at the anal extrem- 



ity, and in this case has gone on sufficiently far to leave the young Starfish riding upon the oral extremity 

 of the Brachiolaria, which alone, with its hrachiolarian and terminal arms, has retained its original shape 

 and proportion. 



24. Bipiimaria asteriijrra. From .Johannes Miiller, Ueber die Larven und die Metamorphose der Echinodermen, 



Zweite Abhandlung, (1S48,) PI. II. Abhandl. d. K. Akad. der Wiss. Berlin, 1849. 



24. A Bipinnaria, 1" in size, seen from the ventral side : 1, upper arm (anal) ; 7, ventral arm (oral) ; S, 3, 4, 5, G, 



dorsal arms ; a, mouth ; h, anus ; d, dorsal vibratile coid ; il', ventral vibratile cord ; c, a', furrow 

 between the vibratile cords of the arms. 



25-28. Asterias gladalis. From S. Loven, Etudes sur les Echinoidees, 1874, PI. LIIl. Kongl. Svenska Vetens. 



Akad. Handl., XL, No. 7. 



25. Young Asterias, 1.3 mm., seen from the ventral side ; a, i, ambulacral plates. 



26. The same, seen from the abactiniil side. In this stage the skeleton is almost exclusively made up of the api- 



cal and of the ambulacral system : a, dorsocentral plate (basal) ; h, interradial plates (genital) ; c, the 

 terminal [dates (ocular). The small |)lates ( ;)) lietween the terminal and the angle of the interradial plates 

 are the first dorsal arm-plates. 



27. Older specimen, 2 mm., seen from the abactinal side ; the single plate (;;) of the preceding figure is replaced 



by a set of three plates. Lettering as before. 



28. Another individual, 4.5 ram., seen from the dorsal side ; one of the genital plates has been pierced by the 



madreporite (r) ; in epch ray a jiair of dorsal water-tubes {t r) have made their appearance. Lettering 

 as for fig. 26. 



