A TAXONOMIC STUDY ON PYROSOMA — METCALF AND HOPKINS. 271 



Plate 24. 



Fig. 21. — Pyrosoma operculatum: Colony, f natural size. After Neumann (1908). 



22. — P. operculatum: A nearly adult zooid, seen from the left side. X13. After 

 Neumann (1908). 



23. — P. operculatum: The end of the cloacal siphon, showing the opercular fold 

 partly closed. X15. After Neumann (1908). 



24. — P. aherniosum: An adult zooid, seen from the right side. X25. After 

 Seeliger (1895). 



25. — P. aherniosum: The viscera of a young zooid (testis immature), seen from 

 the left side. X52. After Seeliger (1895). 



Plate 25. 



Pyrosoma ovation. 



Fig. 26. — The oral end of an adult zooid of the elongated sort, seen from the left 

 side. After Neumann (1913 b). 



27. — An adult zooid of the shorter sort, seen from the left side. XH. Modified 

 from Neumann (1909 b). 



28. — A sagittal section through the distal end of the oral siphon of a zooid of the 

 elongated sort. Xll. After Neumann (1909 b). 



29. — A somewhat ventral view of the distal end of an oral siphon of a zooid of the 

 elongated sort. X24. After Neumann (1913 b). 



Plate 26. 

 Pyrosoma atlanticum atlanticum. 

 Fig. 30. — An adult zooid, seen from the left side. X21. 



Plate 27. 

 Pyrosoma atlanticum atlanticum. 



Fig. 31. — The posterior end of an immature zooid, from a large colony, seen from 

 the left side. X32. 



32. — A young zooid from a small colony, seen from the left side. This was the 

 most nearly mature zooid in the colony. X21. 



Plate 28. 



Fig. 33. — Pyrosoma atlanticum atlanticum: An outline drawing of a ventral view 

 of an oral process of an adult zooid. 



34. — P. atlanticum hawaiiense: A nearly adult zooid, seen from the left side. X15. 



Plate 29. 



Fig. 35. — P. atlanticum paradoxum: An adult zooid, seen from the left side. X21. 

 36. — P. atlanticum triangulum: An adult zooid, seen from the left side. X about 

 11. After Neumann (1909 a). 



Plate 30. 



Pyrosoma atlanticum giganteum. 

 Fig. 37. — An adult zooid from a large colony, seen from the left side. X19. 



Plate 31. 



Pyrosoma atlanticum echinatum. 

 Fig. 38. — A mature zooid of the sort without an elongated oral siphon. X21. 



