BIPENNARIA LAEVJE OF ASTERINA (PATIRIA) MINIATA. 121 



differentiation, became sluggish, and died without having begun 

 to metamorphose. Throughout their lives they remained bilater- 

 ally symmetrical and observations made at the end of the fourth 

 week, shortly before the culture began to die out, showed that the 

 right madreporic pore was still open in several of the largest bi- 

 pennarise. While the larvse were still active and in good health, 

 several specimens were quieted with chloretone and mounted for 



2 3 



FIG. 2. Dorsal view of a somewhat less advanced bipennaria with madre- 

 poric pores close together but both open. 



FIG, 3. Dorsal view of one of the least advanced bipennariae with right 

 madreporic pore closed, but with distinct pore canal on the right side. 



microscopic study. These were drawn with camera lucida and 

 three of these drawings are shown in Figs. 1-3. The largest 

 larva in the culture is shown in Fig. I. Its length was a little 

 over 7 mm. The anterior hydroenteroccel pouches have become 

 completely fused in front of the oral funnel and have grown 

 forward into a median pre-oral ccelomic cavity. The right and 

 left body cavities are equally well developed throughout and each 

 has grown posteriorly beyond its own side and has curled round 



