338 DISCOVERY REPORTS 



Vaughan and C. mabahithi G. and Waugh have 8 systems and no conspicuously com- 

 pressed shape of cahce, this character here appearing to be genetical. 



In this consideration the existence of the pali is helpful, the rule in the genus being a 

 series of larger septa (6, 8, 12, 16 or 24 in different species) without pali, each separated 

 from its neighbour by three septa, the middle one of which has a palus internally — each 

 system has four septa, viz. the dividing septum and these three. There is no great varia- 

 tion in growth,^ but it would seem that the numbers of septa and pali are genetical in 

 each species and that the polyp will build to this end, overcoming by a variety of means 

 all difficulties of growth. 



Of the other characters of Caryophyllia the columella, which exists in all stages of 

 growth, is formed usually of twisted, somewhat flattened rods often termed ribbons, 

 varying in their shape and number with the form and size of the central space between 

 the inner ends of the septa. Sections suggest that there is the formation of one column 

 on the basal plate, additional ribbons appearing as space allows. The presence or absence 

 of costae together with their size and spininess, the exsertness and surface characters 

 of septa, etc., scarcely require comment as these vary greatly with the environment and 

 consequently with the rate of growth of each corallum. An interesting feature of growth 

 is that, with increase of size of the corallum, there is not a proportionate thickening of 

 septa and other parts of the skeleton, although these are covered by the formative tissues. 

 Making certain generally accepted assumptions, such as (i) an increased metabolism 

 of the polyp in proportion to size, (2) the formation of the skeleton in proportion to such 

 metabolism, and (3) the coupling of reproductive activities with a considerable lessening 

 of growth, it is so difficult to understand this cessation of skeleton-deposition that our 

 somewhat mechanical assumptions would appear unjustified. 



1 Sometimes a palus fuses with its septum which then may be classified as the septum of a previous cycle ; 

 the old system divides symmetrically and the two new systems are perfected by the formation of a pair of 

 septa in each; the middle septum of each acquires a new palus. 



