" HUXLEY" FROM NORTH SIDE OF THE BAY OF BISCAY, AUGUST, 1906. 13 



OCULINID^. 



Lophohelia prolifera, Pall. 



Amphihelia oculata, Linn. 



Amphilielia ramea, Miiller. 

 Station VII. Lat. N. 47° 36'. Long. W. T 31'. iJr fathoms. 

 Station XIII. Lat. 48° 7' N. Long. 8° 13' W. 412 fathoms. 



There can be no doubt that the corals obtained by the Huxley at 

 these stations are the same as those obtained by the Porcu^mie at 

 59° 56' N., 6° 27' W., 363 fathoms, and some other localities in the 

 same part of the ocean. Duncan has given a description and several 

 excellent figures of these corals {Trans. Zool. Soc, viii. 1872, p. 330), 

 and commented on their extreme variability. The difficulty of express- 

 ing in a diagnosis in words the difference between the species has not 

 yet been overcome, and after carefully studying his work and that of 

 Moseley {Challenger Reports, vol. ii. p. 178) and of de Lacaze Duthiers 

 {Arch. Zool. Fxpdr., 3", v. 1897), I have been unable to determine what 

 should be, on scientific or historical grounds, the proper limits of the 

 species. The difficulties the systematist finds in dealing with this 

 group are: (1) the great range of variation that each species exhibits 

 in the size of the calices, the manner of growth and ramification of 

 the colonies, the size and even the presence of a columella, the size 

 and the degree of exsertion of the septa, etc. ; (2) the accommodation 

 of the growth of the ccenenchym to the worm-tubes and other objects 

 which the colonies encrust ; (3) the amalgamation of the colonies of 

 the different species. 



(1) As regards the first difficulty, the calices of Lophohelia vary from 

 4 to 15 mm. in diameter across the rim of the calyx, of Am2)hihclia 

 oculata from 3 to 5 mm., of Amphihelia ramea from 2 to 3 mm., the 

 measurements of the larger zooids only of each colony examined 

 being taken. The presence of a columella in Amphihelia cannot 

 be relied upon as a trustworthy character to distinguish that genus 

 from Lopholiclia. On two branches of a colony I regarded as clearly 

 belonging to Amp)hihelia oculata I found that some calices had a 

 columella, others had not, and in others the columella was rudimentary. 



(2) All three species exhibit a remarkable power of forming a 

 growth of ccenenchym over worm-tubes or other objects with which 

 they come into contact. This power (" La puissance blastogenetique " 

 of de Lacaze Duthiers) by determining the character or shape of the 

 support also determines to a great extent the general character of the 

 facies of the colony, and as all three species appear to be partial to a 

 tubular encrusting growth round the tube of the Polychsete worm 



