87 



Distichoptilum gracile, Verrill. Plate IV. fig. 7 ; Plate IX. fig. 2. 



This species is represented b^' a large number of specimens, several of which 

 have a length of 775 mm. ; but all are incomplete. 



The axis is white in colour and very calcareous, varying greatly in diameter, 

 from 0'7-l'5 mm. It is sub-cylindrical, with two opposite sides slightly flattened. 

 Towards the lower end in several sijecimens two grooves are seen ; towards the 

 upper end the shape is nearly quite cylindrical. It is very brittle, and only slightly 

 flexible in the lower part. 



The calices of the autozooids are prominent, l)ut the axial side is closely 

 appressed to and fused with the stem. In the lower part they seem to be arranged 

 in spirals ; but this is soon lost, and they are arranged on opposite sides alternately. 

 The abaxial edge of the calyx is toothed, but in some specimens this is indistinct 

 owing to the state of retraction of the autozooids. The calyx is formed of small 

 needle-shaped spicules arranged parallel to the long axis ; the length varies from 

 1'5 mm. on the lower part of the rachis to 3 '6 mm. in the upper part. On the 

 lower part of the rachis the calices are more crowded than on the upper part ; and 

 the tip of the one reaches to the level of the base of the other ; but on the extreme 

 upper portion of the rachis they are more widely separated. 



In the majority of cases the autozooids are completely retracted within the 

 calices. 



The presence of siphonozooids in close connection with the polyps is an interest- 

 ing feature. According to Verrill, three .siphonozooids occur above each verruca ; 

 Jungersen, on the other hand, from his study of the specimens in the Ingolf 

 Expedition collections, was led to regard the presence of a third siphonozooid as 

 cjuite problematical. From the specimens in the present collection it is evident 

 that the siphonozooids may be two or three. There is one on each side of the calyx 

 at about the same level, and over one of them there is sometimes a third. 



The coenenchyma is thin, allowing the axis to shine through in most of the 

 specimens. Abundant ova are visible in the lower part of many of the auto- 

 zooids. 



The spicules are slender, smooth but fluted rods tapering slightly to both 

 ends, but ending bluntly. The following measurements were taken of length and 

 breadth in millimetres: "3x0 "02; 0"3x0'04. There are smaller, more oval 

 forms, "04x0 "02. All the spicules are exceedingly brittle. In colour they vary 

 from a very pale to a deep sherry tint. The u}iper portion of the abaxial wall of 

 the calyx is reddish, all other parts are yellowish or yellowish-white. 



In many of the specimens an embryo was found towards the base of the re- 

 tracted autozooid on tlie abaxial side. The embryo is a flat circular disc from 

 0"52-0"55 mm. in diameter; the ova are spherical, from 0"15-0"2 mm. in diameter. 



Locality : Station 231 ; T 34' 30" N., 76" 08' 23" E. ; 836 fathoms. 



