MEMOIRS OF THE NATIONAL A.CADEMY OF SCIENCES. 



445 



stage ii ro the Fdwardsise. The resemblance between the mesenteries characteristic of this group, 

 and those appearing in the course of the development of the A.ctinian larvae, was recognized by 

 Haddon (1889), and the stage was termed by McMurrich (1889) the " Fdwardsia-st&ge." The 

 eight complete mesenteries, comprising two bilateral pairs (I, II) unci two pairs of directives 

 (111. IV), are often spoken of collectively as the Edwardsian mesenteries. 



1'ntil recently the adult Edioardsia was supposed to have no other than these eight complete 

 mesenteries, and in this respect was considered to be one of the simplest of the Actiniaria. As 



EC E 



Fig. 4. 

 Diagrammatic figures showing the relationship c if the polyps to the axis in various colonial Anthozoa. The upper side of the figure is supposed 

 to be toward the axis (axial) and the lower is away from the axis (abaxial). a, Madrepora. The sulcaror ventral aspect of the p<>lpy is 

 axial and the sulcular or dorsal is abaxial. < The upper of the two bilateral pairs marked V, V should have been VI, VI.) b, Most other 

 Madreporarian species. The sulcular aspect is axial and the sulcar abaxial. c, Zoanthids. The gonidial groove orsiphonoglyph is 

 abaxial. and all the metacnenies ( A-D) are added at this aspect, d, Alcyonaria. The siphonoglyph is abaxial. 



such it has been regarded by Boveri (1889) and McMurrich (1891) as the starting point for the 

 diverse modifications occurring within the different Actinian groups. Lately Faurot (1895), by 

 making transverse sections through the uppermost region of the capitulum of Eohoardsid 

 beaittempsi, has shown that in this species sixteen and even twenty mesenteries are present, 

 corresponding with the same number of tentacles. The eight additional mesenteries were found 

 to be feebly developed, but arranged on the normal Hexactinian plan, and to extend vertically 

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