PYROSOMA. 



FIG. 150. Pyrofvma giganleum.I. A vertical section of the wall of the Aecidiarinm 

 near the cloaca] aperture and including its lip. II. The youngest condition of a 

 bud before the ectoderm is elevated. III., IV., V. Further ?tape of the develop- 

 ment of a hud. VI. A fully-formed bud with a second ascidiozoflid in course of 

 development from its peduncle. 



