FIG. 20. Hypolytkius call/codes. C4, nerve ganglion; H, 

 heart ; M, the position of the atriopore. The large open- 

 ing on the upper side is the mouth. (From a drawing by 

 Professor Moseley in Herdman's* Tunicata of the "Chal- 

 lenger " Expedition.') 



L 



