Manchester Memoirs, Vol. Ixi. (i9i6\ No. I. '^J^ 



more cylindrical. On the lower branches the ix)lyps are mainly 

 confined to two sides (the smaller or lateral sides), and thus 

 there is a fairly large median area without polyps. Towards 

 the apex of the colony, the polyps tend to become more uni- 

 formly disposed on all sides, especially is this the case m the 

 smallest terminal branches. Clearly defined grooves or lines 

 (5 or 6) are present on the lower part of the colony, on those 

 surfaces free from polyps. These grooves become much less 

 obvious towards the apices of the branches, and there only one 

 or two lines occur, or they may be absent. These lines are 

 clearly visible tO' the naked eye, especially on the lower part 

 of the colony. 



The colony is about 13.2 cm. in height, and 14.2 cm. in 

 breadth. The height of the main axis previous to the origin 

 of any branches is 2.65 cm., and its diameter at the middle 

 2.5 mm. The primary branches which originate from this have 

 a diameter of 4 mm., including the polyps, and 2 mm. without 

 the polyps. The bare areas without polyps on the lower 

 branches are about 2 mm. wide. The apical branches are about 

 2 mm. in diameter, including the polyps. 



The distribution of polyps is as stated above, but even 

 near the base polyps occur occasionally on the surface of the 

 coenenchyme, which is usually free from polyps ; on the other 

 two surfaces the calyces are slightly elongated in the direction 

 of the long axis of the colony, and the openings are slightly 

 slit-like in appearance. In most cases the polyps are not com- 

 pletely retracted, and the tentacles may be seen in white, re- 

 lieving the yellow ground colour of the calyces and coenen- 

 chyme. 



The distance between the polyps varies, sometimes they are 

 separated by an interval of i millimetre, at other times they 

 are so closely adjacent as to be only a fraction of a millimetre 

 apart. The polyps may measure 2 mm. in one diameter, 1.2 mm. 

 in another, and 1.2 mm. in height. In the polyps situated on 

 the apical branches the opening is easily seen lying longitudinal 

 to the long axis of the branch. The longitudinal grooves or 

 lines on the lower part of the colony are about i mm., and the 

 slight elevations between them about .7 mm. in breadth. The 

 encrusting base measures 1 1 mm. in diameter and 3 mm. in 

 height. The coenenchyme covering the central cylindrical axis 

 is about 0.1 mm. in thickness, and does not increase to any 

 extent in the higher reaches of the colony. 



The surface of the colony is densely covered with small 

 spicules. On close examination it is seen that the longitudinal 

 grooves have a smaller number of spicules than the elevations 

 between them. Two of the branches end in apical swellings, 

 on which the polyps are thickly distributed ; one of the swell- 

 ings is 7 by 6 mm., the other g by 6 mm. ; these may possibly 

 be due to regrowth after injury. 



On that part of the basal column which has no polyps 



