PLATE XII. 



LETTERING ON THE FIGURES. 



col. w., column wall. 



c. is., cell-islet. 



c. s., ciliated streak (Fimmerstreif) . 



cm., cuticle. 



d., directives. 



disc, disc 



ect., ectoderm. 



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



ect. m., ectodermal muscle layer. 



enc. s., encircling sinus. 



end., endoderm. 



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



fb. I., fibrillar layer. 



fos., fossa. 



gl. c, gland cell. 



g. gr. gonidial groove. 



g. s. , glandular streak. 



(Driisenstreif , Nesseldrii senstreif ) . 



inc., incrustations. 



i. s., intermediate streak. 



lac., lacuna?. 



m., mesentery. 



m. fil., .... mesenterial filament. 



lines., mesoglcea. 



mg. st marginal stoma. 



mr. m macrocnemic mesentery. 



nem., nematocyst. 



nr. I nerve layer. 



ob. in., oblique muscle. 



p. b. m., .... parieto-basilar muscle. 



per. St., .... perioral stoma. 



»-. ect., .... reflected ectoderm. 



r. m., retractor muscle. 



r. s., reticular streak. 



s. d., sulcar directives. 



sl. d.. sulcular directives. 



sp., spermarium. 



sph. m., .... sphincter muscle. 



St., stomodaeuru. 



tent tentacle. 



zoox., zooxanthellae. 



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



Figure 



1. Ricordea florida. Transverse section through the stomodasal region of a polyp in which the 



niesoglceal plaitings for the support of the retractor muscle are displayed, as also the irregular 

 development of the pairs of mesenteries of the third order. Three pairs of perfect mesenteries 

 occur on the one side of the directives and four pairs on the other, x 12. 



2. Ricordea florida. Transverse section through a portion of the column-wall and a mesentery of 



the first order, x 320. 



3. Actinotryx Sancti-Thoma. Transverse section through a fertile mesentery with ripe spermaria in 



act of dehiscing, x 75. 



4. Homostichanthus anemone. Plan of tentacular arrangement. An outer series of cycles in which 



the same number of tentacles occurs in each endocoele and exocoele can be distinguished from 

 an inner series in which the cycles are imperfect, and more separated one from the other. 



5. Homostichanthus anemone. Eadial section of portion of column-wall, x 320. 



6. Homostichanthus anemone. Tangential section through the periphery of the disc and uppermost 



region of the column-wall. The portion represented is but slightly tangential, so that only 

 two mesenteries are cut through, and two tentacles are in communication with an exocoele 

 and two with an endoccele. The mesogloeal plaitings supporting the restricted sphincter 

 muscle are a little longer in a truly radial section than are here represented, x 25. 



7. Corynactis myrcia. Plan of tentacular arrangement. 



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