360 MR. S. PACE ON THE 
position and grows up in advance of its daughters, so that it is 
at all stages the terminal polyp of the colony, in Turbinaria the 
parent polyp bends away from its first daughter-bud and then 
grows up together with and alongside its daughters, so that 
eventually it comes to form one of a ring of calicles of which its 
daughters are the other members. 
While the central area of the cup is typically wholly ecenen- 
chymatous, occasional examples are met with in which a calicle 
does occupy a central position within it; but, as already stated, 
this is a very unusual occurrence, and it would appear to be the 
result of a secondary torsion on the part of either the parent or 
of one of the daughter polyps. I have also noticed in a few 
specimens the existence of a slight central elevation which 
rather suggested that a calicle was buried at that point; but as 
no dissection was made, it may well be that the appearances 
observed were in reality due to the presence of some commensal 
or parasite. 
The Variation of the Corallum. 
A few words regarding some of the modifications which the 
Turbinarian cup undergoes with advancing age, and by the 
direct influence of its environment, may not be out of place, 
since I have had rather exceptional opportunities * for the ob- 
servation of corals and their habits, and since the so-called 
species of Turbinaria have been to so large an extent founded 
upon what are in reality but acquired characters. Bernard, in 
his Catalogue of the British Museum Turbinarie, found himself 
obliged to group them according to the forms ultimately assumed. 
by the cup; but, inasmuch as it was obvious that many of these 
might be adaptational or even accidental, he pointed out that his 
classification was purely morphological, and only to be regarded 
as a provisional one. It will now be my endeavour to show that 
the variations of a Turbinarian colony from the primitive cup- 
shape—the “ crateriform” type of Bernard—can be readily ex- 
plained by reference to the conditions under which the coral has 
* During a stay of nearly three years in Torres Straits, while engaged in the 
investigation of the commercial pearl-shell, some thousands of examples of 
Turbinaria in all growth-stages have passed through my hands or under my 
notice. Turbinarians are exceedingly plentiful on the reefs in this region, and! 
young individuals, as well as large cups, are very commonly found on the- 
backs of the pearl-shell collected by divers. 
