PLATE 28. 



Porpita pacifica. Figs. 1-10, 12, 16. Porpema prunella. Figs. 11, 1.5. 



Porpita umbella. Fig.s. 13, U. 



Fig. 1. General view of a specimen 50 mm. in diameter from above. From a photograph. 



Fig. 2. A segment of the upper sm-face of the pneumatophore and limbus, to show the promi- 

 nences (Pr) and stigmata (Sti). From a photograph. X 4. 



Fig. 3. A segment of the upper surface of the centradenia, with the pneumatophore stripped off. 

 T, tentacle. From a photogi-aph. X 3.5. 



Fig. 4. Central region of upper surface of float, to show the pahal canals. From a photograph. 

 X9. 



Fig. 5. A segment of the hmbus with its canals (C. Li) and marginal mucous glands (Gl. Mu). 

 C. pa, palial canal. X 12. 



Fig. 6. A portion of one of tlie canals of the limbus. X 40. 



Fig. 7. Roof of central chamber and first cu'cular chamber of the pneumatocyst, from below, to 

 show the aborted primary stigma (Sti') opening from the former, and the aborted secondary stigmata 

 (Sti-) from the latter. Reconstructed from serial sections. X 40. 



Fig. 8. Vertical section tlirough central part of pneumatocyst; Ch, central chamber; Ch. C, 

 circular chamber; Sti, primary stigma. From a photograph. X 40. 



Fig. 9. Vertical section through the aborted primary stigma; more enlarged. X 150. 



Fig. 10. A dissection showing the extremities of the superior canals of the centradenia (C. S), from 

 above; C. Li, canals of the hmbus. X 12. 



Fig. 11. Porpema prunella. Roof of the central gastrozooid, seen from below, to show the open- 

 ings of the inner and outer series of the centradenia canals (C. Ce', C. Ce^). Reconstructed from serial 

 sections. X 20. 



Fig. 12. Porpita pacifica. Extremity of a mature tentacle. X 5. 



Fig. 13. Porpita umbella. Segment of the pneumatophore and limbus. From a photograph. 

 X8. 



Fig. 14. Porpita umbella. Portion of the hmbus, with its canals. X 20. 



Fig. 15. Porpema prunella. Section through the endoderm wall of one of the superior centradenia 

 canals. X 250. 



Fig. 16. Porpita pacifica. The centre of the centradenia, from above. X 20. 



