CERIANTHARIA. ce 



himself in manifest contradictions. On page 12 (1908) he says "J'appelle (in Ceriantharia) anterieure 

 I'extreniite de I'actinostome que les actinologistes ont appelee ventrale; elle est caracterisee par la 

 presence du tentacnle marginal median, de la loge directrice et du sillon actinopliaryngien, que je 

 designe, avecHaddon sous le nom de sulcus. J'appelle posterieure la commissure buccale qtii repond 

 a la loge de multiplication, toujours depourvue de tout teutacule, appelee dorsale par les auteurs recents". 

 On page 196 speaking of Zoauthidae he calls the directive chamber by which tlie siphonoglyph is 

 situated, the anterior: "Dans les deux larxx-s I'iucurvation est telle que la coucavite de la courbe 

 repond a la face anterieure, c'est a dire a la loge directrice". He tlius makes lujmologous to each 

 other the siphonoglyiDh and directive mesenteries whicli are disparate in Ceriantharia and Zoan- 

 tharia, and considers them to be ventral or anterior. On page 165 van Beneden maintains an- 

 other view. After insisting that the mesenterial musculature in Ceriantharian larval forms is by no 

 means uniformly arranged (see mesenterial musculature) he continues "Rien ne prouve done que 

 I'hypothese de Carlgren soit fondee et il n'existe actuellement aucnne donnee qui nous permette 

 d'affirmer Thomologie du sulcus des Cerianthides avec la rainure actinopharyngienne, dite ventrale, 

 des Zoanthes et des Hexactiniens". Here then all homology is denied between the siphonoglyph of 

 Ceriantharia and that of Zoantharia. Witli the latter statement the following remark of van Beneden 

 is also in conflict (p. 164). "II en resulte que la partie du corps qui prend naissance (in Zoantharia) 

 dans la seconde periode se forme par opposition, non pas d'arriere en avaut, comme chez les Ceri- 

 anthides, niais d'avant en arriere". 



It is clear that we cannot call the siphonoglyph of the Cerianthidae, sulcus, if we maintain 

 the view, that no homology exists between the siphonoglyph of the Cerianthidae and that of Zoau- 

 thidae or the ventral one of Actiniaria (Hexactiniae), for by denominating the siphonoglyph of Ceri- 

 anthidae sulcus and not sulcnlus, we ipso facto make the siphonoglyph of Cerianthidae homologous 

 with the siphonoglyph of Zoauthidae and with the ventral one of Actiniaria. For we must remember 

 tliat the actinologist who introduced the designation sulcus into the terminology of the Antliozoa, 

 namely Had don, applied tlie term sulcus to the so-called ventral siphonoglyph of Actiniaria (Hex- 

 actiniae), and the term sulcnlus to the so-called dorsal one of that group. If then we deny all 

 homology between the siphonoglyph of Cerianthidae and either of the siphonoglyphs of Actiniaria, 

 we naturally cannot call the siphonoglyh of Cerianthidae either sulcus or sulcnlus. 



Now it is very probable that the directive plane is similarly situated in all Authozoa, because 

 the Anthozoa, as far as our knowledge goes, are a very homogeneous group. If tlien we take the 

 directive plane as the basis of orientation, we have to determine how far the directive mesenteries 

 in Ceriantharia are ventral or dorsal, or, in other words, how far the single siplionoglyph in tliis case 

 is ventral, and therefore a sulcus, or how far it is dorsal, and tlierefore a sulcnlus. To answer tins 

 question, we can only make use — as far as I can make ont — of the anatom\- and tlie development 

 of the mesenteries, for the physiological orientation of the siphonoglyph to the bottom gives us no 

 fixed standpoint for judging of the homology. 



To take first the morphology of the mesenteries, the disposition of the mesenterial musculature 

 plays, as is well known, an essential part in the orientation of the mesenteries of Actiniaria and other 

 Anthozoa, as in tlie S-mesentery stage the longitudinal nnusculature of the mesenteries on either side 



