Remnant of 

 notochord 



Stomach ^^i '^ 



Heart -^ 

 Atrium 



Mouth 



. Adhesive papillae Remnant of 

 notochord 



Anus 



Mouth 



Orifice 

 Atrium 



Remnant of nerve cord 



Mouth 



Mouth 



'Brain" 



Mouth 



Endostyle 

 Gill slits 



Anus 



Stomach '^X^~'^(^'.''^ — -^ 

 E 



Endostyle 



Atrium 



Heart 



Fig. 18.4. Successive stages in the metamorphosis of an ascidian, from the attachment of the 

 tadpole larva to the establishment of the adult form. Note particularK the desteneration of 

 the tail and notochord, the extreme reduction of the nervous system, and the change in orienta- 

 tion of the mouth and digestive tract. (Redrawn, after various authors, from Y. Delate and 

 E. Herouard, Trade de zoolo^ie concrete, 1898, vol. 8.) 



548 



