PLATE 27. 



Porpema prunella. 



Lettering as in Plate. 26. 



Fig. 1. Transverse section of corm near base of tentacular zone. At X the section passes through 

 a parasitic treniatode. From a photograph. X 20. 



Fig. 2. A portion of wall of section shown in fig. 5, pi. 26, more highly magnified. From a re- 

 touched photograph. X 80. 



Fig. 3. Similar section at level of fig. 6, pi. 26. From a photograph. X 40. 



Fig. 4. Portion of the same more highly magnified to show the connection between the tentacular 

 canal (C. T) and the endoderm of the centradenia, and relationship between the cnidoblast mass of the 

 centradenia (X) and the ectoderm of the pneumatosaccus (Ec ^). From a photograph. X 80. 



Fig. 5. Radial section through apex of the pneumatophore. Ce, centradenia. Other lettering 

 as in PI. 26. From a photograph. X 50. 



Fig. 6. Section through apex of pneumatophore showing cell layers and stigmata (Sti', Sti=). 

 X about SO. 



Fig. 7. I.,ongitudinal section through base of corm, showing the centradenia of one of the canals 

 (C. Ce) by which it connects with the margin of tlie central gast rozooid (Gz) . From a photograph. X 40. 



Fig. 8. A similar section, showing the open lumen of the canal. From a photograph. X 40. 



Fig -9. A similar section, showing one of the canals (C. Ce) of the inner series wliich connect with 

 the gastrozooid (Gz). From a photograph. X 40. 



Fig. 10. Longitudinal section of the wall of the central gastrozooid. From a photograph. X SO. 

 Longitudinal section through a young tentacle, to show histology. From a photograph. 



Apical view of a model of the centradenia, constructed by the plate process. X 40. 

 Apical view of centradenia, reconstructed from serial sections, showing the superior 

 canals (C. S) and trachea (Tr). X about 80. 



