270 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Plate 15. 



Pyrosoma atlanticum. 



Fig.1. — A schematic figure of a zooid, showing internal organization. After 

 Burghause (1914'. 



Plate Iti. 



Pyrosoma agassizi. 



Fio. 2. — An oral view of the mouth region of a zooid, showing tentacles, sphincter 

 muscles, lateral muscles, nervous system, peripharyngeal bands and tip of endostyle. 

 Alter Neumann (1909-1913). 



3. — A nearly adult zooid, seen from the left side. X 25. 



Plate 17. 



Pyrosoma agassizi. 



Fi(i. 4. — A posterior view of a nearly adult zooid. X 25. 



5.— The nervous system, exclusive of the oral region. After Neumann (1909-1913). 



Plate 18. 



Pyrosoma agassizi. 



Fig. 6. — The open end of a colony. After Ritter and Byxbee (1905). 

 7. — A young zooid, seen from the left side. X 42. 



Plate 19. 



Pyroso ma sp in os urn. 



Fig. S. Au adult zooid, seen from the left side. X 17. 



Plate 20. 



Pyrosoma spinosum. 



Fig. 9. — A postero-ventral view of the posterior end of an adult zooid. X 21. 

 10. — -The reniform vesicle and adjacent organs, seen from the left side. X 28. 



Plate 21. 



Fig. 11. — Pyrosoma spinosum: A, an embryo with uusegmented stolon. X 18 

 B, an embryo with the four primary ascidiozooids appearing as buds upon the stolon 

 X56. 



12. — P. verticillatum: An adult zooid, seen from the left side. X 21. After Neu- 

 mann (1909c). 



Plate 22. 



Fig. 13. — Pyrosoma verticillatum: The oral region of a zooid, showing chiefly the 

 nervous system. After Neumann (1909-1913). 

 14. — P. verticillatum cylindricum: Colony. X 2. 

 15. P. verticillatum cylindricum: An adult zooid, seen from the left side. X 21. 



Plate 23. 



Fir,. Id. — Pyrosoma hybridum: Colony. X 2. 

 17. — P. hybridum: An adult zooid, seen from the left side. X 21. 

 18. — P. ellipticum: An adult zooid seen from the left side. X 21. 

 19. — P. elliptic a m: Colony. Natural size. 



20. — P. ellipticum: The same colony as that shown in figure 19, seen from the open 

 end. Natural size. 



