PLATE XVII. 

 THE BRANCHIAL SAC. 



1. Ascidia mentula Miill. (p. 78) 



2. A', rubicunda Hanc. (p. 84) 



3. A. rubrotincta Hanc. (p. 86) 



4. A. crassa Hanc. (p. 90) 



5. A. mollis A. & H. (p. 93) 



6. A. plana Hanc. (p. 96) 



7. A. Alderi Hanc. (p. 99) 



8. A. rudis Alder (p. 101) 



9. A. producta Hanc. (p. 106) 



10. A. inornata Hanc. (p. 109) 



11. A. depressa A. & H. (p. 112) 



12. A. elongata A. & H. (p. 113) 



All the figures much enlarged, but reduced in various pro- 

 portions from Mr. Hancock's drawings. 



