250 
ectoderm and the mesenterial filaments, as is found in several Antipatharia, is entirely absent 
in the Ceriantharia. 
Roule places the Antipatharia at the base of the Anthozoariae, i. a. while they are not 
truly bilaterally symmetrical organisms, viz. where “l’organisme produit ses parties principales, 
et les oriente d’emblee, symetriquement par rapport a un plan median; il les conserve ainsi” 
(Roule: 14, p. 45), but binarily symmetrical, which is a sort of bilateral regulation of an 
organism, which at first was radial. The structure of the Antipatharia is radial, but they 
become binarily symmetrical through the flattening of the actinopharynx, which, in its turn, 
causes a disproportion between the median and the lateral tentacles and interseptal chambers. 
1 he flattening of the actinopharynx is caused by the colonial mode of living; the polyps 
stretch out at right, angles with the colony-axis, to be no hindrance to each other. Although 
1 agree with Roule that the Antipatharia are not reduced organisms, I have some objections 
to the latter arguments. I he polyps of the Antipatharia are elongated in the direction of 
the colony-axis, sometimes to an exceedingly high degree; it is not clear how this fact is to 
be combined with an elongation of the polyps in a sagittal direction, to give no hindrance. 
Besides the Cerianthus-larvae are binarily symmetrical, in Roule’s sense, and scarcely the adult 
Ceriantharia are bilaterally symmetrical. With these Cerianthus-larvae there is no question about 
colony-formation; in what manner is the binaril symmetricy to be explained in this case? — If, 
on the other hand, Roule will call the Cerianthus-larvae truly bilateral, I see in this fact a new 
difference with the binarily symmetrical Antipatharia, so that the relation between the Antipatharia 
and the Ceriantharia is lessened, opposite to Roule’s opinion. 
b 01 the rest, Rolle remarks that the Antipatharia may be called primitive, while the 
oecology as well as the bathymetrical and the zoogeographical distribution indicate a great age 
of the Antipatharia. 
While the differences between the Antipatharia and' the Ceriantharia are too great to 
pei mit the combining of them to Cerianthipatharia, there is much to say in favour of the thesis 
that the Antipatharia are primitive organisms. As one of the most important arguments in 
ia\ our of the opinion that the Antipatharia are reduced organisms is given, that the secondary 
mesenteries descend deepest on the side of the actinopharynx. The mesenteries of the Antho¬ 
zoariae take origin at the side of the bodywall and reach the actinopharynx later on, so that 
they are shorter at the side of the actinopharynx. But with the Antipatharia I find that the 
secondary mesenteries in most cases descend deepest at the side of the bodywall, while the 
sixth pair of Euciwipcithes contovtci as well as all the mesenteries in Schizopctthcs ajji'yiis are 
fixed at the side of the bodywall, while they do not reach the actinopharynx at all. This facts 
are more in accordance with a new appearance of mesenteries than with a reduction of existent 
mesenteries. Besides the sixth pair of mesenteries is the only one which can not bear muscle- 
fibres and so is probably of younger origin; the few facts which could be obtained as to the 
succession in development of the mesenteries, indicate that the secondary mesenteries appear 
ahei the primary ones and that the sixth pair is developed at a later stage of development of 
the young polyps than the other mesenteries. 
