REPOET ON THE ACTINIARIA. 87 



2, p. 74; Zoophytes, j)l. ii. fig. 2), is certainly attached to a smooth underlying substance, 

 but is, nevertheless, greatly elongated in one direction, so that, if we may judge from the 

 drawing of it, even the corona of tentacles is divided into a right and a left half. On the 

 other hand, Gephyra dohrnii, our knowledge of which we owe to G. v. Koch (Zur Phylo- 

 genie der Autipatharia. Morphol. Jalirb., Bd. iv., Suppl., p. 78, 1878), settles like a true 

 Amjshianthid on the axis of Isis elongata. The animals either live singly or are united 

 by basal processes into a colony ; they are fastened to the axis by a cuticular mass secreted 

 by the pedal disk. The author has unfortunately given no details as to the position of 

 the oral fissure with respect to the axis of the Isis and the constitution of the sej)ta and 

 oesophageal grooves. 



G. V. Koch considers the Gej^hyrce as transition forms between the Actiniaria and the 

 Autipatharia ; he assumes that Actinite settled upon cylindrical bodies and secreted a 

 horny mass by which they attached themselves, that later, from want of a foreign axis, 

 they originated a proper axial skeleton by richer secretion of the adhesive mass, and 

 moreover became branched by forming colonies. The correctness of this view is con- 

 firmed by the few remarks made by v. Koch on the structure of Antipathes larix. The 

 body is elongated in the direction of the skeletal axis, and the transverse axis of the 

 animal thereby appears lengthened, whilst the sagittal axis is shortened. This I conclude 

 from the position of the mouth and the septa ; the former is either circular or fissure- 

 shaped ; if fissure-shaped, it crosses the longitudinal axis of the animal. The difi"erent 

 direction of the longitudinal axis of the body, and the oral fissure is very striking, but can 

 be easily understood if we assume that the oral fissure has maintained its original exten- 

 sion in a sagittal direction whilst the body is prolonged in a transverse direction. We 

 must therefore look for the directive septa on the long sides of the body. In fact, we 

 find there two pairs of septa, which correspond to the oral angles, are sterile, and conse- 

 quently comport themselves like directive septa, whilst the two remaining pairs, lying 

 in the prolonged transverse axis, bear reproductive organs, and are therefore best termed 

 accessory septa. 



It is therefore most probable that the Amphianthidse bring about the transformation 

 of the Actiniaria to the Autipatharia. A more detailed study of the Anti^^atharia is 

 however necessary before this view can be fully accepted ; above all, it must be deter- 

 mined whether the paired arrangement of the septa and the presence of the directive 

 septa can be demonstrated in the Autipatharia, and whether the sagittal and the trans- 

 verse axes are directed in the same manner as in the Amphianthidse. 



Stephanactis, n. gen. 



Amphiautidse with firm wall, divided by a circular swelling into an upper and a lower 

 section ; tentacles numerous, arranged in several rows, decreasing in size from within 

 outwards. 



