36 THE VOYAGE OF H.M.S. CHALLENGER. 



stomodseum is supported by a number of mesenteries 1 (sareosepta) which incompletely 

 divide the ccelenteron into a number of radial chambers. The mouth is rarely round, 

 most frequently it is slit-like, the long axis being placed at right angles to the axis of 

 the branch on which the zooid is situated. The axis corresponding with the elongation 

 of the mouth will be spoken of as the " sagittal " axis, that at right angles to it as 

 " transverse." I have not been able to note any well-marked siphonoglyphe in the various 

 species examined, though, on account of the small size of the zooids, these would be 

 difficult to make out in preserved material, even should they exist. 



The tentacles arise from the margin of the peristome, or some form the peristome and 

 others form the body-wall. In the Antipathinse there are always six tentacles present. 

 These are simple finger-like outgrowths of the ccelenteron. In the Schizopathinae each 

 zooid bears only two tentacles, but in this subfamily the zooids are dimorphic, and three 

 zooids correspond morphologically with an unspecialised zooid of the ordinary type. 

 In Dendrobrachia the tentacles are branched. 



The mesenteries, on account of their different relative development, may be conveniently 

 considered under two heads, viz., "primary" and "secondary." This division is, 

 however, artificial, and is merely used for convenience of description. 



In all Antipathidse the primary mesenteries are six in number, and are well developed. 

 The secondary mesenteries are developed in a varying degree in different genera. Of 

 those already examined the number is six or four, or the series may be entirely wanting. 

 The number, arrangement, and comparative length of the mesenteries may be best 

 studied by means of a series of horizontal sections commencing at the oral surface.. The 

 number of mesenteries in the oral cone generally differs from that in the lower section of 

 the ccelenteron. The arrangement in the various genera will be best understood by 

 reference to the diagrams. 



o 



Leiopathes. 



This genus may be conveniently taken first on account of the fact that, as the 

 mesenteries are present in a multiple of 6, it is more directly comparable than other 

 genera with the regular Hexactinise. In Leiopathes glaberrima the mouth is somewhat 

 elongated in the sagittal axis, whilst the zooid is elongated in the transverse axis. In 

 neither case, however, is the elongation so pronounced as in some other forms. 



A horizontal section through the upper portion of the oral cone (fig. 1) shows that 



1 I have used the term mesentery in the present Report in preference to septum or sarcoseptum, because, whatever 

 objection there may be to its use in reference to the Anthozoa, it has within that group a well-defined meaning. It is 

 solely applied to the soft radiating partitions passing from the body-wall to the stomodreum, which imperfectly divide 

 the ccelenteron into chambers. In addition to these in Antipathida- the individual zooids are imperfectly separated 

 from one another by means of vertical mesoglceal partitions, to which the terms septa and sareosepta might be considered 

 equally applicable, but which would not come within the meaning of the term mesentery. 



