PLATE I. 



Figs. 1-3. Pyrosoma atlanticum. 

 Figs. 4-21. Pyrosoma giganteum. 



at. Atrial aperture. 



cm. Masses of phosphorescent cells. 



en. Endostyle. 



i. Intestine. 



i.l. Internal longitudinal bars. 



m.h. JIuscle bands. 



n.rj. Nerve ganglion. 



ce. (£sophagus. 



2>.p. Peripharyngeal bands. 



uph. Sphincter muscle. 



tn. Tentacles. 



tn'. Large ventral tentacle. 



t.c. Test cells. 



tr. Tranverse vessel of branchial 

 sac. 



Fig. 



Fig. 

 Fig. 



1. Section of open end of colony of Pyrosoma atlanticum from off Cape Verde, 

 showing condition of diaphragm ; natural size. 



2. Circle of tentacles from Ascidiozooid of same colony (8. I). 



3. Part of longitudinal section of same colony, showing atrial apertures opening 



into common cloacal cavity (S. 1). 

 Fig. 4. Section of open end of colony of Pyrosoma giganteum from off Cape Verde, 



showing condition of diaphragm ; natural size. 

 Fig. 5. Part of section through the surface layer of test of same (S. \). 

 Fig. 6. Part of section through deeper part of test of same (S. \). 

 Fig. 7. Part of branchial aperture of Ascidiozooid of same (S. \). 

 Fig. 8. Branchial apertures and processes of test of same ; natural size. 

 Fig. 9. Free edge of diaphragm of .same, showing numerous muscle bands (S. l). 

 Fig. 10. Part of last more highly magnified (S. \). 

 Fig. 11. Muscle fibres from mantle of same (S. \). 

 Fig. 12. Part of branchial sac of .same (S. l). 

 Fig. 13. Part of branchial sac, showing irregularity (S. 1). 

 Fig. 14. Part of internal longitudinal bar of same (S. \). 

 Fig. 15. Part of transverse vessel of same (S. \). 

 Fig. 16. Edges of one of stigmata of .same (S. |). 

 Fig. 17. Part of branchial .sac of same (S. \). 



Fig. 18. Anterior end of Ascidiozooid of same, from branchial sac (S. \). 

 Fig. 19. Part of anterior end of branchial sac of same, from side (S. 1). 

 Fig. 20. Some of the phosphorescent cells of same (S. \). 

 Fig. 21. Alimentary canal of a young Ascidiozooid of same (S. l). 



