PYROSOMA. 



523 



r* 



Fig. \h§.—Pyro$oma giganteum.—l. A vertical section of tlie wall of the Ascidiarium 

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

 hnd hefore the ectoderm is elevated. III., IV., V. Further stages of the develop- 

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

 development from its peduncle. 



