398 



Comparative Morphology of Chordates 



/ATRIAL CAVITY/ SPINAL CORD 



UROCHORDATE LARVA. 



^ENDOSTYLE 



,GILL SLITS 

 CILIATED FUNNEL| j\ ,ATRIAL CAVITY 



BRAIN\ 

 MOUTH\ 



\notochord 

 intestine 

 heart B _ ME TAMORPHOSIS. 



Fig. 307. Diagrams of stages in the metamorphosis of a urochordate larva. 

 When the larva settles down and becomes fixed by its adhesive papillae, the tail is 

 lost and the notochord disappears. Thus the chordate characters which are so evi- 

 dent in the larva are partly lost in the mature animal. (Redrawn from korscheldt 

 and Heider, after Seeliger. Courtesy, Neal and Rand: "Chordate Anatomy," 

 Philadelphia, The Blakiston Company.) 



Fig. 308. A tunicate, As- 

 cidia, attached to a stone; seen 

 from right side. Arrows indicate 

 the oral (incurrent) and the 

 atrial (excurrent) openings. 



