72 



ing from a sketch (not reproduced) from a living specimen there are 

 only two transverse connections between the two halves of the body 

 skeleton not three as in Heliocidaris tuberculata; this point, however, can- 

 not be settled, the skeleton having been dissolved in the preserved speci- 

 mens of the young larva (while it has remained perfectly intact in all 

 the other stages preserved). 



The fully formed larva (PI. I, Figs. 1-2; textfigure 26) is provided 

 with four well developed vibratile lobes, but has no epaulets. The anal 

 area is rather deeply concave. The postero-lateral processes are short. 



Fig. 25. Larva of Echinometra lucunter, 2 days old, showing skeletal structure. A. seen 

 from the ventral side; B. side view. ^"U. Letters as in fig. 20. Further: oe. mouth; 



re. rectum; St. stomach. 



earshaped. In the larva in beginning metamorphosis (when the first pedi- 

 cellaria has appeared in the midline in the posterior end) the vibratile 

 band in the constriction above the postero-lateral processes widens to- 

 wards the midline, so that it has almost the appearance of forming a 

 closed ring round the posterior end of the body. Whether it may ulti- 

 mately form a really closed ring I have been unable to ascertain. Also 

 the vibratile lobes gradually become so broad as almost to join in the 

 midline of the body and thus to form an apparent transverse band about 

 the middle of the body. Along the dorsal side the vibratile band is 

 raised into a pair of lobes, supporting a wall across the dorsal side of the 

 body. At the anterior edge there may be a pair of small processes formed 

 by the vibratile band, where it bends from the preoral over to the antero- 



