PLATE XL 



LETTERING ON THE FIGURES. 



eol. w column wall. 



c. is., cell-islet. 



c. s., ciliated streak (Flimmeratreif). 



cu., cuticle. 



d., directives. 



disc, disc. 



ect., ectoderm. 



ect. can., .... ectodermal canal. 



ect. m., .... ectodermal muscle layer. 



e>ic. s., encircling sinus. 



end., endoderm. 



end. m., .... endodermal muscle layer. 



/5. I., fibrillar layer. 



/os., fossa. 



gl. c, gland cell. 



g- gr., gonidial groove. 



g. s., glandular streak. 



(Driisenstreif, Nesseldriisenstreif ). 



inc incrustations. 



%. s., intermediate streak. 



lac, lacunae. 



m., mesentery. 



m. fil., .... mesenterial filament 



tnes., mesoglcBa. 



mg. St., .... marginal stoma. 



mr. »!., .... macrocnemic mesentery. 



nem., nematocyst. 



nr. I., nerve layer. 



ob. m., oblique muscle. 



p. b. m parieto-basilar muscle. 



per. St perioral stoma. 



r. ect., .... reflected ectoderm. 



r. m., retractor muscle. 



r, s., reticular streak. 



s. d., sulcar directives. 



si. d., sulcular directives. 



s.p., spermarium. 



sph. »!., .... sphincter muscle. 



St stomodiEum. 



tent, tentacle. 



zoox., zooxanthellae. 



I., n., III., &c., . . orders of mesenteries or tentacles. 



Figure 



1. Phymanthus crucifer. Transverse section through a portion of the column-wall and a mesen- 



tery of the first order, and one of the mesenteries of the fourth order, taken a little below 

 the stomodseal region, x 320. 



2. Phymanthus crucifer. Transverse section through a trilobed mesenterial filament, x 320. 



3. Actinotrijx Sancti-Thoma;. Vertical section through the upper region of the column-wall, showing 



the mesoglojal plaitings for the support of the sphincter muscle, x 250. 



4. Actinotryx Sancti-Thoma;. Transverse section through a mesenterial filament, just below the 



stomodaeal region. One of the large nematocysts is represented in longitudinal section and 

 another in transverse section, x 250. 



5. Ricordea florida. Plan of tentacular arrangement. The members of the outermost cycle are in 



the same radial areas as the inner tentacles, and alternate with those of the next cycle 

 within. The arrangement in orders is not very regular in larger polyps. 



6. Ricordea florida. Transverse section through the stomodajl region to show the irregular arrange- 



ment of the mesenteries, and the columnar and stomodseal mesoglceal processes. Only a 

 few of the columnar processes are represented, x 12. 



7. Stoichactis helianthus. Plan of tentacular arrangement in a young specimen. The members 



of the outermost cycle communicate with the exocoeles and alternate with all the radial rows, 

 which are endocoelic. 



8. Actinoporus elegans. Plan of tentacular arrangement. 



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