MADREPORARIAN CORALS 45 



feature of the case is that, owing to the similarity in minute 

 structure of tlie coenosteum of the two genera, all trace of 

 the line of fusion is lost. 



In both these genera anastomoses of the branches, 

 formed in the same manner by the grafting of one colony on 

 another or of one branch with another, frequently occur, 

 giving rise to great tangled masses of coral branches, with 

 various kinds of worm-tubes and shells deeply imbedded in 

 them (Fig. 5, p. 28). 



To write an accurate description of such a mass would 

 require a great deal of time and patience, as it might consist 

 of three or four species, each showing a great range of varia- 

 tion in the size of the calices and the characters of the septa 

 and columella, all of which would have to be carefully 

 studied before an approximate estimation of the number of 

 individual corals that have taken part in the composition 

 of the masses could be made. 



The only account of the living polyps of these two genera 

 that we possess is that of de Lacaze-Duthiers. In both 

 genera the living tissues are very transparent, but show a 

 pale yellow colour, which is more pronounced round the 

 mouth and on the oral disc. The tentacles correspond in 

 number with the septa, and vary in size according to the 

 order of the septa above which they are situated, the tentacles 

 above the primary septa being larger than those above the 

 secondary septa, and those, above the secondary septa larger 

 than those above the tertiary septa. They have a pale 

 yellow colour and are speckled with white spots representing 

 nematocysts or groups of nematocysts, and at the extremity, 

 which is pointed, these spots are so numerous and closely 

 grouped together that the tentacle seems to have a bright 

 white tip. Minor differences between the genera observed 

 by de Lacaze-Duthiers are, that in Lophohelia the tentacles 

 are relatively shorter and thicker than in Amphihelia, and 

 that the size of the tentacles in the former is more irregular 

 as regards the order of the septa than it is in the latter. 

 Fowler has also pointed out that in Lophohelia there are no 

 directive mesenteries, but that in the Amphihelia they are 

 present. 



