22 PERCY SLADEN TRUST EXPEDITION 



conspicuous rim. Over the attachments of the mesenteries the ectoderm is raised up into 

 ridges which differ in width, thickness and shape in the different species, these characters 

 being of specific importance. By the presence of these ridges, longitudinal furrows 

 (" sillons actinopharyngiens " of van Beneden) are formed. In the genera of Group I 

 below, characterised by the presence of two couples of directive mesenteries and both 

 bilateral and radial symmetry*, two loiigitudinal grooves are present facing the directive 

 couples of mesenteries, being usually deepened by the folding of the stomodseal wall into 

 the directive entocoeles. The stomodseal ectoderm is ciliated, but the cilia do not appear 

 to be longer in either of the grooves, nor is the ectoderm lining them specially thickened. 

 Although these grooves are not so pronounced in my sections as the so-called sulcus 

 of Peachia or the sulcus and sulculus of Bunodcs, they are not less evident in transverse 

 sections than the same grooves in some examples of Edwardsia and Zoantlms that I have 

 examined (they are well seen in my sections of Echinopora lamellosa, Lej^tustrea 

 Toissyana and Gcdaxea fascicularis). On the other hand, Duerden denies the existence 

 of any such groove ("siphonoglyph") in the Madreporaria (21, p. 23); Bourne also is 

 inclined to take the same view. Duerden further says " a siphonoglyph is generally 

 wanting only in the lowest actinians and in alcyonarians, and its absence in coral polyps 

 would suggest their more primitive nature." These two grooves are here termed directive 

 grooves t, as they lie in the directive entocoeles ; none of the other names hitherto 

 employed to denote them in the Anthozoa are suitable for coral polyps. 



Great confusion prevails over the orientation of Actinian polyps and in particular 

 over the terminology employed to denote these two grooves. HoUard in 1851 (p. 274) 

 referred to them as "deux demi-canaux " ; Gosse in 1860 (p. 4) termed them "gonidial 

 grooves (canales gonidiales) " ; the Hertwigs in 1879 distinguished them as "ventral" 

 and "dorsal," following upon KoUiker's (1872) use of "ventral" for the side of a 

 Pennatulid polyp turned towards the stem and "dorsal" for the opposite side. Following 

 Haddon objection may well be raised against the extension of these terms to the 

 Actinise. In 1884 Andres (p. 73) substituted "gonidium" and "gonidulum" for 

 Gosse's gonidial grooves. Hickson in 1883 (p. 693) invented " siphonoglyph e " for the 

 ciliated groove of Alcyonarians which is said to be homologous with the single groove of 

 Peachia and the ventral grooves of other Actinians ; Parker (110) in a foot-note on p. 260 

 drops the final e with Hickson's assent, as etymologically unnecessary ; both he and 

 McMurrich apply " siphonoglyphs " to the two grooves in Actinians. 



Haddon in 1889 (p. 300) introduced "sulcus" for the more important groove of 

 Actinians (viz. ventral groove of the Hertwigs) and "sulculus" for the opposite (dorsal) 

 one. Haddon's nomenclature, which has been accepted by Bourne, van Beneden and 

 others, is as objectionable as the Hertwigs' "venti-al" and "dorsal" when applied 

 to adult Actinians in which there is no recognisable difference in the size of the two 

 grooves. The distinction between ventral and dorsal, sulcar and sulcular, may be 



* Boveri (18) uses biradial symmetry to denote the combination of both the bilateral and radial symmetry 

 in Actinians. 



t Perhaps Faurot's commissural grooves ("sillons commissuraux ") and commissural mesenteries maybe 

 preferable to "directive grooves" and "directive mesenteries." 



