HiCKSON — Notes on a Small Collection of Hydrocorallince. 501 



This similarity in the gouophores of AUopora and Sti/laster^ 

 the presence of twelve tentacles (the number attributed by Moseley 

 to the gastrozooids of Allojwva) in the gastrozooids of S. gracilis, 

 and many other points in their anatomy support very strongly 

 the statement that " the separation of the genera AllojJora and 

 8t//laster is difficult." 



It is quite possible that Stylaster has been derived from a form 

 closely resembling AUopora by the terminal branches remaining 

 in their development more delicate, and showing consequently 

 more definitely than in the ancestral type the regular alternate 

 method of gemmation. 



DISTICHOPORA. 



Several specimens of Bistichopora were placed in my hands by 

 Professor Haddon, some of them well preserved in spirit, after 

 treatment with corrosive sublimate, the others dried. All the 

 specimens were obtained in shallow water off Murray Island in 

 December, 1888, and January, 1889. The first point that 

 attracted my attention was the great variety of colour exhibited 

 by the specimens. Some of the smaller colonies are bright orange 

 in colour, others Vandyke brown, and the larger ones are deep 

 purple with pale yellowish white tips. Many intermediate 

 varieties of colour are to be met with in the collection (PI. xviii.). 



These diiferences of colour do not mean a difference of species. 

 All the specimens should be referred to Lamarck's Distichopora 

 violacea. The differences in colour do mean, I believe, a difi:'erence 

 in age and sexual condition. I do not like to speak too confi- 

 dently on this point, because the number of specimens at my dis- 

 posal is not sufficiently large, but I think it will be proved when the 

 varieties of Distichopora of this region are more fully investigated : 



1. That the young colonies of not more than half an inch in height 

 are usually bright orange in colour and are not sexually mature. 



2. That the colony turns brown later in life, and male ampullae are 



formed ; and, 3, that the older colonies reaching on an average an 



inch and a-half in height and four or five inches across the longest 



diameter of the flabellum are violet. Local causes, such as the 



position with regard to other corals on the reef, depth of water or 



tide eddies may cause some colonies to turn violet sooner than 



others, or, indeed, to become sexually mature before the colour 



2R2 



