MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



445 



stage are the Edwardsiic. The resemblance between tlie mesenteries characteristic of this group, 

 and those appearing in the course of the development of the Actinian larvfe, was recognized by 

 Haddon (18S9). and the stage was termed by McMurrich (1889) the " ^^7*/v//Y7.v/«-stage." The 

 eight complete mesenteries, comprising two biliitoi'al paii-s (I, II) and two pairs of directives 

 (III, IV), are often spolcen of collectively as the Edwardsian mesenteries. 



Until recently tlie adult Eihrardfla was supposed to have no othei' than these eight complete 

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



E E 



Fig. 4. 

 Miagrammivlip flgurcs showing the relationship of tlic polyps to the axis in various colonial Anthozoa. The upper side of the figure issupposed 

 to be toward the axis (axial) and the lower is away from the axis (abaxial). a. Madrcpom. The sulcaror ventral a.spoct of the polpyia 

 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 oraiphonoglyph is 

 abaxial, and all the metacneme.s (.^-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 Edumrdnia 

 hfauteiiipxi, has shown that in this species sixteen and even twenty mesenteries are pi'e.sent, 

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

 to be feeblj- developed, Init arranged on the normal Hexactinian plan, and to extend vertically 

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