CERIANTHARIA. ,q 



In the first .sub-order he includes not only the forms that posses "acontia" but also those which in 

 the adult state are known not to posses any, e. g. Ceriantlius mciiibroiiacrus and several species of 

 Pacliyccriantluis. As far as I can see, INIc. Murrich has here fallen into error, for there is nothing 

 in the development of the Ceriantharia to point to the "acontia" being- larval organs, that afterwards 

 disappear in the full-grown individuals. On the contrary it is possible that the "acontia" in some cases 

 shew themselves quite late in the course of development, and most i)rol)ably their number increases 

 with the growth of the animal. In reality Mc. Mur rich's diagnosis ol Acontiferae conflicts seriously 

 with van Bene den's. 



Whilst Mc. Murrich says of Acontiferae that "they are provided with acontia at lea.st during 

 the early stages of development", we find in van Beneden's diagnosis of the three genera ^o^wAv- 

 acfis^ Apiactis and Pcponacfis, that the acontia are "absentes on tardives", a view quite contrary to 

 ;\Ic. Mur rich's. As we know besides that the majority of Ceriantharia, so far anatomically des- 

 cribed, lack acontia and botrucnidae alike, we have at once a strong reason for removing these Ceri- 

 antharia from the group Acontiferae. It seems to me necessary therefore to expel the whole of Mc. 

 Mur rich's Cerianthidae family, and a great part of the Arachnactidae family as well, from Acon- 

 tiferae, thus reducing it so considerabh', that it would only be found to include .some adult form.s. 

 In my opinion then Cerianthidae should be divided into three group.s. 



(1) those that possess neither botrucnidae nor "acontia". 



(2) those that possess "acontia" but not botrucnidae. 



(3) those that possess botrucnidae but not "acontia". 



To the first group belong Mc. Murrich's Cerianthidae and a part of his Arachnactidae. 



Mc. Murrich divided Acontiferae into 2 families Cerianthidae and Arachnactidae. In the 

 former the second couple, reckoning from the directive chamber, would he the longest mesentery 

 couple (the telocnemes) of the protomesenteries, in the latter famih- on the other hand the fourth 

 couple would be "the telocnemes". This characterisation does not seem to me quite .satisfactory even 

 if we apply it only to the two adult genera included by Mc. Murrich, Ccriaiitlnis and Pachycrri- 

 authits, and this among other reasons because the fourth couple in my opinion belongs not to the 

 protocnemes but to the metacnemes (deuterocnemes, metamesenteries). Between Ceriantlius and Pacliy- 

 ccr III u thus, which are doubtless real genera, there is a distinct difference however, as Mc. Murrich 

 has clearly recognized, namely, that whilst in the genus Ceriantlius the second couple of protocnemes 

 is long, fertile and similar to the metacnemes of the ist cycle {M), in the genus Pachycerianthus on 

 the other hand, the same couple is short, sterile, and provided with a well developed cnido-glandular 

 tract like the metacnemes of the 3rd and 4th cycles [B, b). 



Mc. Murrich 's diagnoses, too, of the genera Ceriantlius and Pachycerianthus are not so distmct 

 as might be wished. As to the genus formulated by Roule and accepted by Mc. Murrich, Pachy- 

 cerianthus, it is extremely difficult to form from Roule' s description an adequate idea of the mesen- 

 terial appendages (the filaments and the "acontia"), with whicli it is far more important to be ac- 

 quainted than with some of the generic characters mentioned by Roule. Roule (1904) characteri.ses 

 the genus in this way "cloisons courtes, deux seules d'entre clles (S3 = fourth couple) parviennent 

 dans I'extremite aboralc. Cloisons directrices epaisses donncnt a la lage directrice la forme d'un canal 



