314 DR. J. E. DUERDEN ON THE 



The three agree in such important characteristics as the presence of an ectodermal 

 columnar and stomoda;al muscle- and ganglion-layer, the absence of gonidial grooves, the 

 absence of a basilar muscle and of a well-developed parieto-basilar and endodermal 

 sphincter muscle, and the presence of ciliated bands on tlie mesenterial filaments. 



In accordance with these later results, the definition of the genus Butiodeojjsis may be 

 emended as follows : — 



Genus Bunodeopsis, Andres. 



Actiniaria with ciliated flattened base, feebly adherent. Column-wall beset proximally 

 with simple or complex, sessile or pedunculated evaginations, bearing large thick- walled 

 nematocysts ; distal part of column smooth and delicate. Column with ectodermal 

 and endodermal muscle- and ganglion-layers ; sphincter muscle very feeble or absent. 

 Tentacles elongated, deciduous, separated from the polypal cavity by a circular perforated 

 septum provided with a sphincter muscle. Disc with thickened lips and circumoral 

 sphincter muscle. Stomodaeum with ectodermal muscle and ganglion-layers, without 

 gonidial grooves. 



Mesenteries normally liexamerovis, two pairs of directives, more than six com^jlete 

 pairs, often irregularly developed. Parieto-basilar muscle very feeble. Basilar muscle 

 absent. Mesenterial filaments with ciliated bands. Without acontia and cinclides. 



Prom the foregoing account it is clear that, while in many I'espects B. (jlobulifera 

 possesses primitive Actiuian characteristics, yet in others it is highly difi"erentiated. If 

 the conclusions of Carlgren (1900) as to the nature of the primitive Actiniae be correct, 

 amonir the former must be reckoned the occurrence of an ectodermal columnar and 

 stomodaeal muscle- and nerve-layer, the absence of gonidial grooves from the stomodaeum, 

 the absence of a basilar muscle, and the weakness of the internal musculature generally. 

 Among the latter will be included the division of the column into two distinct regions, 

 of which the upper is naked, and the lower bears liollow evaginations with the ectoderm 

 broadened and charged with thick-walled nematocysts ; the occurrence of a tentaculo- 

 coelomic septum provided with a sphincter muscle ; the circumoral ectodermal thickening 

 (lips) charged with thin-walled nematocysts ; the circumoral endodermal sphincter 

 muscle ; and tlie regional differentiation of growth of the tentacles and mesenteries. 



The first-mentioned characters are those upon which Carlgren has founded the Tribe 

 Protanthete, which includes the lowest Actiniae, as contrasted with the Tribe Nynantheae, 

 under which are placed all the more differentiated Actinii3e. Carlgren regards as the 

 most important characteristic of the Protantheae the presence of the ectodermal longi- 

 tudinal muscle- and nerve-layer in the column- wall, and gives second place to the absence 

 of the basilar muscle. Wherever the first-mentioned structures occur, Carlgren would 

 separate their possessors from the forms witli whicla they have been associated, and jilace 

 them under the Protanthete, whatever the other characteristics of the sjjecies might be. 



In a forthcoming report on the Porto Kican Actinians, to be published by the 

 U.S. Pish Commission, I have discussed these proposals somewhat, so that it is 



