too 



Comparative Morphology of Chordates 



Atrial cavity Pharynx 



Mouth 



Anus 



Intestine i 



Stomach 



^•y "SSSS 



Fig. 310. Doliolum, a free-swimming tunicate. The somewhat diagrammatic 

 figure, taking advantage of the fact that the thin body-wall of the small animal is 

 semitransparent, assumes that the main features of internal structure may be seen 

 through the outer wall. The many branchial slits (stigmas) through which water 

 passes from the pharynx into the atrial cavity are not shown, but are suggested by 

 arrows. The animal's swimming movements are effected by contractions of the 

 circular muscles. 



Fig. 311. Appendicularia (Fritil- 

 laria) fwcata, from the ventral surface. 

 (a) Anus; (gl) unicellular glands; (gs) 

 gill-slits; (h) dorsal hoodlike fold of 

 integument; (m) mouth; (/) tail. 

 (After Lankester. From Willey: "Am- 

 phioxus and the Ancestry of the Verte- 

 brates." By permissionof The Mac- 

 millan Company, publishers.) 



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