XVII 



PEOTOCHOEDATA 



643 



intestine are developed from a third Imd, which arises from the old 

 oesophagus just where the epicardial Imd joins it (Fig. 468, D) ; and 



oes' 



oes 



oes 1 



oes* 





int* ep 



FIG. 468. Four stages in the budding of, a Diplosoiuid Ascidian. (After Pizon.) 



A, the oozooid (i.e. the organism produced by the metamorphosis of the larva) has produced by 

 separate buds a new pharynx and oesophagus and a new intestine. 15, the new organs ihave greatly 

 increased in size. C, the pharynx of the oozooid is reduced to a degenerate mass, its oesophagus and 

 intestine have disappeared, but the second pharynx has produced by budding a I bird pharynx ; a second 

 stomachic loop has been produced. D, the third pharynx has increased in si/e and has developed an 

 oesophagus and a third intestine has been produced. A second heart has been produced from the second 

 pharynx, and the second stomachic loop has become functional. < ./.< endostyle; ,</i, epicardial out- 

 growths from second pharynx ; H\, //_>, the hearts ; inn, hit-, hit", the intestinal rudiments; 01*1, oes", 

 ops 3 , the oesophageal rudiments ; j>/i', />//-, ;>/V ; , the three pharynxes ; at ] , at-, t he t wo stomachs. 



so a compound organism arises with two branchial sacs joining in a 

 common gut, which then bifurcates into two intestinal buds, which 

 reunite at their distal ends, only to bifurcate again into two recta. 





