490 SYDNEY J. HICKSON. 



The size and shape of the spicules vary considerably. In young anthocodiae, as for 

 example on D (Fig. 9), the largest spicules of the points were 0'5 mm. x 0*04 mm., and 

 the spicules of the crown 0"5 mm. x 001.5 mm. In older anthocodiae, as for example on F, 

 they were respectively 0-6 x '08 and 0-5 x 0-4, and in E 07 x 0085 and 05 x O'OS (Fig. 10). 



The spicules of the points in E might be described as tightly packed, a large number 

 being wedged into the basal part of the triangle, and in the crown the greater stoutness 

 of each spicule causes them to lie much closer together than in the crown of D. This 

 tight packing of the spicules of the older specimens renders the anthocodiae much less 

 retractile than in the younger specimens. There is another series which is less regular. 

 The spicules of the anthocodiae of the youngest specimens are usually white, or pale yellow, 

 those of the oldest purple. It is usually in the purple specimens that we find the tightest 

 packing of the spicules. Thus in D the spicules are white, in F orange, and in E purple. 

 It seems a reasonable proposition to suggest that the colouring matter of these spicules 

 changes from white to purple as the colony approaches the light, or as they increase in age, 

 and that the noticeable variations in the series are due to local differences in surroundings. 



Before comparing Ghironephthya variabilis with the species C. dipsacea, G. scoparia, and 

 C. crassa of Wright and Studer (22), it may be pointed out that these authors do not 

 state definitely that the measurements given below refer to the largest spicules of the polyps, 

 but it is probable that this was their intention. 



Crown 

 S])iciiles 



Point 

 Spicules 



If Wright and Studer's measurements refer either to the greatest size or to the average 

 size of the spicules in these situations it is clear that the range is much greater between 

 C. dipsacea and G. crassa than it is between any two examples that I have studied in 

 this collection. As regards the arrangement of the spicules Wright and Studer state that 

 in G. dipsacea and G. scoparia the spicules of the points are arranged in a A-shaped 

 manner, but no detailed description or figure has been given. 



I may say, however, that from a careful examination of the type specimens in the 

 British Museum I am convinced that the arrangement of the spicules of the points in all 

 three of the Challenger species is essentially the same as it is in G. variabilis mihi. There 

 are variations in size and in crowding as in the Maldive specimens, but the four principal 

 spicules of the points can be recognised in most of the anthocodiae I examined. Turning 

 now to the question of the colour. A glance at the type specimens of the Challenger 

 species shows how variable is the colour of the spicules. The description given by the 

 authors is accurate so far as it goes, but as a matter of opinion it does not appear to 

 me to give enough detail of the differences in colour between branch and branch of the 

 same specimen, or the gradual fading of one colour into another on the stem, as to do 

 full justice to the subject. I think that any impartial naturalist who carefully examined 

 these specimens would say that colour is a character of very little value in the attempt 

 to separate these three species. 



It is not my purpose to go fully into the accounts given of the arrangement of the 



