THE DEVELOPMENT OP ECHINOIDS. 339 



EXPLANATION OP PLATE 33, 



Illustrating Mr. E. W. MacBride^s paper on " The Develop- 

 ment of Echinoids." 



Lisi of Abbreviations employed. 



a. ep. Anterior ciliated epaulette, an. Anus. coe. coelomic sac. Ech. Rudi- 

 ment of oral disc of young Echinus, fr. Frontal area. m.p. Madreporic pore. 

 ped. Pedicellaria;. p. ep. Posterior ciliated epaulette, pig. Mass of green 

 pigment, pr. prce. o. Prseoral process of ciliated band. pr. ant. hit. Antero- 

 lateral process, pr. post. dors. Postero-dorsal process of the ciliated baud. 

 pr. post. 0. Post-oral process of the ciliated band. [These last four names are 

 Mortensen's notation for the pluteus arms.] red. Intestine. 



The magnification of all the figures is about that obtained by a Zeiss, obj. A, 

 oc. 2. 



Fig. 1. — Larva of Echinus mi liar is six years old, side view. Note the 

 prseoral lobe {fr.) overhanging the mouth. 



Fig. 2. — Larva of Echinus miliaris in the second week, dorsal view. 

 rect. Intestine, an. Anus, seen through ; third pair of arms beginning to 

 appear. 



Fig. 3. — Larva of Echinus esculentus seven days old, dorsal view. 

 Commencement of third pair of processes. 



Fig. 4. — Larva of Echinus miliaris three weeks old, dorsal view. ped. 

 First rudiment of a pedicellaria. pig. Characteristic green pigment. 



Fig. 5. — Larva of Echinus esculentus three weeks old, dorsal view. 

 Ech. First trace of oral disc of adult. 



Fig. 6. — Larva of Echinus esculentus four weeks old, dorsal view. 

 p. ep. Posterior ciliated epaulettes. 



