'53 



EXPLANATION OF PLATES I-IV. 



All the figures refer to Flahelluin riihrnm unless otherwise 

 stated, ect. Ectoderm, c. ccf. Calicoblast ectoderm, end. Endo- 

 derm. s I. Structureless lamella. 7i. /. Nervous layer of the 

 ectoderm. /. ii. Tentacular nematocysts. end. n. Reduced 

 endodermal nematocysts. in. ^. c. Mucous gland cells. 

 g. g. c. Granular gland cells, f. h. Ingested foreign bodies. 

 /. g. Fat globules, m. f. Muscular fibres. 



Fig. I. Section of the calicoblastic ectoderm on the side of 

 a septum about i mm. inside the edge against the axial fossa. 



Fig. 2. Section of the attachment of the body- wall to the 

 corallum at the base of a mesentery. 



Fig. 3. Section of the body- wall over a septum near its 

 upper free edge. 



Fig. 4. Section of the ectoderm of the external body-wall. 

 (The section is that of a knob caused by the contraction of 

 the polyp. It serves to show the constituents of the layer, 

 but does not give in any way a real idea of its true appear- 

 ance. It was chosen only alter a prolonged search, no other 

 section in this position showing more than i nerve cell and 2 

 or 3 granular gland cells. The vacuolated nature of the 

 layer does not appear). 



Fig. 5. Section through a battery of nematocysts on a 

 partially retracted tentacle. 



Fig. 6. .Section through the ectoderm of the stomodoeal 

 wall over the attachment of a mesentery. 



Fig. 7. Section of the stomodoeal wall between the attach- 

 ments of two mesenteries. 



Fig. 8. Transverse section of the mesenterial filament and 

 edge of a primary mesentery at about the middle of its course. 

 (For the sake of clearness no tone has been placed over the 

 structureless lamella). 



Fig. 9. Reduced endodermal nematocyst, reconstructed 

 from a series of sections. 



Figs, 10-15. Various stages in the development of the 

 corallite. The numerals where present refer to the cycles of 

 the septa. 



Fig. 16. Scar of a broken-off corallite. The dark lines in 

 the septa are depressions, due to the eating away of the 

 corallum along the central " dark lines " of the septa. 



