518 Mr. H. M. Bernard on the 



calicles which appear to be the typical normal calicles of the 

 specimen. Great variations may occur even in these points, 

 according to the position of the calicle and according to its 

 degree of protuberance ; but, if due caution is used, a number 

 of good taxonomic characters are thus at hand for use. 



On the Inftuence of Position on the Character of the Calicles. 

 — A great field of investigation is here opened up. I am not 

 referring primarily to the effects of variations in the direction 

 and in the force of the currents and in the quantity of nutri- 

 tion received, all of which, no doubt, play an important part, 

 but to modifications of form due to internal causes, notably to 

 the streaming of the nutrient fluids in the canal-system, I 

 have already pointed out that the streaming of the coenen- 

 chyma is a factor of prime importance in the building-up of 

 the corallum. This streaming is sufficient in many cases 

 actually to submerge living calicles, which, in some cases, 

 may again break through or else apparently put out a number 

 of secondary buds. In other cases the polyps have con- 

 tinually and progressively to lengthen, in order to keep at 

 the surface of the coeuenchyma ; and while calicles situated on 

 rounded knobs are often abnormally large and protuberant, those 

 on erect fronds project but slightly. These facts, taken together 

 with the fact that the canals of the coenenchyma are in open 

 communication with the polyp-cavities, appear to me to make 

 it highly probable that, just as this flow builds up the coenen- 

 chyma and gives it its appearance of streaming, so it must 

 also affect the skeleton of the calicle itself, through which it 

 doubtless runs. Indeed, in some cases it appears as if the 

 calicles have to be protected against this. In coralla where 

 the downward streaming is very marked by the deep regu- 

 larly parallel furrows, these, in descending, are turned to right 

 and left whenever they reach a calicle, converging again 

 below it. 



This is no fanciful question, but one which may prove o£ 

 profound significance ; for if, in any single coral, the down- 

 ward flowings of the coenenchyma can in any way affect the 

 morphology of the polyp, this would have to be taken into 

 account in any attempt to classify the corals according to the 

 type of the polyp. The differences found in the soft parts of 

 the polyp may be secondary and adaptive to the physiological 

 conditions resulting from the forms of the coralla and to the 

 streamings of the contents of the canal-system. 



The Coenenchyma. — This intercalicular tissue is very pro- 

 minent in Turbinaria. It is, as we have seen, comparable 

 in every essential with the coenenchyma of Madrepora and 



