EXPLANATION OE PLATE IX— Continued. 



ElG. 6. — Oral gastric endoderm from the same specimen as that from wliich 

 fig. 5 is taken. The larger secretion-cells appear to have been shed 

 and to have left, the intercellular spaces (/) unoccupied. New secretion- 

 cells (b) are projecting from the intercellular trabeculge {d), and will 

 probably fill up the vacant spaces as they increase in size. 



EiG. 7 . — Diagrammatic vertical section of the oral gastric endoderm of fig. 3. 

 Letters as in fig. 3. 



EiG. 7'. — Diagrammatic vertical section of the proximal or ingestive endo- 

 derm of fig. 1. Letters as in fig. 1. 



EiG. 8. — Junction of the ingestive endoderm with the endoderm of a radial 

 canal. 



w, endoderm of the radial canal. Other letters as in fig. 1. 



EiG. 9. — Endoderm of the gonads, showing the polygonal outline of the 

 cells and the block-like deposits within their substance. 



PLATE X. 



Fig. 1. — Endoderm of the middle region of the gastric tube. 

 a, nuclei; b, secretion-cells ; yj intercellular spaces. 



EiG. 2. — Endoderm of the middle region of the gastric tube, consisting of 

 uniform hexagonal-cells. 

 ff, embedded nematocysts. 



EiG. 3. — Surface view of a tentacle of the smallest size, to show the 

 grouping of nematocysts. 



EiG. 4. — Optical section of a small tentacle in a plane including the long 

 axis. 



6, endoderm-cell ; c, structureless lamella closely adhering to the 

 endoderm-cells ; d, layer of muscular processes of the ectoderm -cells ; 

 e, endoderm-cells with nematocysts. 



EiG. 5. — Actual transverse section of a tentacle. 



a, rudimentary lumen (probably due to the shrinking caused by 

 reagents). Other letters as in fig. 4. 



EiG. 6. — Nematocysts with extruded thread. 

 a, completely, b, incompletely everted. 



