THE EDWARDSTA-STIGE OE LEBEUNTA, 307 



of the Antliozoa to the Enterocoela. Having established, both 

 experimentally and histologically, that the digestive functions o£ 

 the Alcyonaria are confined to the six ventral mesenterial fila- 

 ments, he regards the latter as the representatives of the alimen- 

 tary canal of higher animals, and suggests that " they are not only 

 physiologically but also morphologically the equivalents of the 

 enteron of the Enterocoela"; and continuing, atfirms that 

 "morphologically we may regard the radial chambers as diverti- 

 cula from the primitive enteron." 



Van Beneden (1891), from his study of the development of 

 the larval Cerianthid Arachnactis, likewise comes to the same 

 conclusion in reference to the mesenteric chambers of the 

 Anthozoa and the coelomic diverticula of the higher animals- 

 He devotes special attention to a comparison of the origin 

 and arrangement of the mesenteries and their chambers in the 

 Cerianthidge with paired coelomic diverticula of the segmented 

 Metazoa. 



According to a preliminary notice appearing in ' Nature,' 

 March 2, received when this conti'ibution was nearly completed, 

 Mr. J. Stanley Gardiner, studying a supposed new species of the 

 coral Coenopsammia from Lif u, has also come to practically the 

 same conclusion as Prof. E. B. Wilson in regard to the enteron 

 and mesenterial filaments. The notice contains the pertinent 

 sentence : " It was further contended that the stomodgeum 

 together with the mesenterial filaments is homologous with the 

 whole gut of the Triploblastica, and that the so-called endoderm 

 is homologous with the mesoderm. The Actinozoon polyp then 

 must be regarded as a Triploblastic form." 



In the larva of Lehrmiia we appear to have the actual embryo- 

 logical proof of these surmises, founded mostly upon a con- 

 sideration of the adult anatomy. And it is clearly such a problem 

 as can only be established on embryological grounds. 



Whether the larval spaces are derived originally as paired or 

 radiating evaginations of the terminal region of an archenteron, 

 and their walls are then to be regarded as mesothelium or endo- 

 derm, or whether they originate as splittings within the solid 

 undifferentiated cell-mass, matters but little. Both processes 

 occur in the higher animals : in some the ccelome originates from 

 endodermic diverticula, e. g. Echinodermata, Amphioxus ; in 

 others from mesoblastic splitting, e. g. nearly all Vertebrates. 



