PYROSOMA. 



523 



*•» 



Fig. 150.— Pyrosoma giganteum.—l. A vertical section of the wall of the Aecidiarium 

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

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

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

 development from its peduncle. 



