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



delicate lines arranged somewhat radially around the lumen. The subjects of oogenesis 

 and spermatogenesis in the Antipatkidse will be discussed in detail in a subsequent 

 paper. 



Antipathella contorta. 



At present I only propose to refer to one point in the structure of this species, viz., 

 to the situation of the ova. All the specimens examined contained ova in various stages 

 of development, but in this species they are apparently larger and less numerous than 

 in any other species of the genus which has come under my notice. The largest 

 observed have a diameter of 0*34 mm. From two to five ova, according to their size, 

 cause a considerable dilation of the lateral sections of the ccelenteron, which is very 

 marked in horizontal sections. In several cases I was able to satisfy myself that the 

 ova are contained within mesoglceal capsules (as in Schizopathmse), and not within a 

 thickened mass of entoderm, as appears to be the case in Antipathella subpinnata. 

 In sections of a mesentery, at a point where it contains only one ovum, the mesoglcea on 

 leaving the body-wall consists of a single thin layer up to the point where the ovum is 

 situated. Here it becomes split up into two portions, which completely surround the 

 ovum, and then ultimately become united again beyond the ovum into a single layer. 

 At the free margin of the mesentery the mesoglcea again becomes divided into two 

 portions, which form a short transverse bar at right angles to the breadth of the 

 mesentery. The whole is clothed with a layer of entoderm, which, however, is thinner 

 around the ovum than in other portions of the mesentery. Here evidently the ova are 

 developed under the same conditions as in Actiniaria. They arise from entodermal 

 cells, but undergo their elaboration within the mesoglcea. 



Antipathes dichotoma. 



The polyps of Antipathes dichotoma, and apparently also of other species of the 

 genus (e.g., Antipathes arborea and Antipathes virgata), are larger than those of any 

 other ramose Antipathina? known at present. The general form of the polyp and the 

 arrangement of the mesenteries has already been described (p. 41). The ova are con- 

 tained in a speciabised band of cells stretching across from near the lateral margin of a 

 polyp to the lower portion of the stomodaeuni. Its situation is best understood from a 

 study of transverse vertical sections (PL XIV. fig. 1). The band contains a median 

 strand of mesoglcea continuous with that of the body-wall and stornodseum, and on each 

 side is a layer of entoderm of the usual structure. The ova are apparently enclosed 

 within semi-fibrous capsules united to the layer of mesoglcea which passes the whole 

 length of the band. Simple or branched ribbon-like mesenterial filaments occupy 



