Remarks upon the general Structure of the Heliolitidae. 



The coenenchyma is the raost prominent feature of the Heliolitida\ Numerous are 

 the names which have been bestowed upon that part of the composed corallum in this 

 family and others, and quite as much varied have been the interpretations concerning 

 its true nature. 



LiNN^Us spöke about »pori miniini» between »pori magni», Hisinger says »massa 

 porösa cellulis interjecta», James Hall »spaces between the openings», Dana »interstitial 

 space», Phillips »intervalls filled by polygonal openings», M'Coy »polygonal tubes», Lons- 

 DALE »interstices» or »interstitia porösa». German authors as Schlottheim say »Zwischen- 

 räume», Quenstedt »Zwischenmasse» or »Grundmasse», Vogt »Zwischensubstanz» and most 

 recently von Koch »Zwischengewebe». 



In this state of an unstable and ever changing terminology, it was most welcome, 

 when Milne-Edwards and Haime in their grand works on the structure of the Corals 

 put an end to the confusion by giving the questionable structure a new definition and 

 denomination. In their first memoir ^ they have called it peritheca. Identical is probably 

 also the »tissu commun des Astrées» which they called »exothéque ^. The term »coenen- 

 chyma» appears for the fii'st time in their monographic descriptions of the Astra^ida; '''. 

 It is there stated that »ces cötes réunies entré elles par des traverses nombreuses, förment 

 tout autour de la muraille des divers individus une masse celluleuse plus ou moins 

 épaisse, d'ou résulte un coenenchyme * ou tissu commun dont le développement est sou- 

 vent trés-considérable». 



The best definition is that given by the same authors in the »Introduction to the 

 British Fossil Corals» (1850 p. vi). It is according to them the calcified derm which ex- 

 tends »exteriorly without constituting distinct costaj, and forms a dense or reticulate 

 tissue, which in certain aggregate corals, is nowhere referable to any individual polyp 

 and produces a sort of intermediate mäss or true coenenchyma». Intercostal dissepiments 

 also assume »the appearance of a coenenchyma, or common tissue». 



1 Ann. Sci. Nat. Zool. 3:e Serie, vol. IX, p. 49. 



2 \. c. p. 84. 



ä Ann. Sci. Nat. 3:e Serie, X, p. 213. 1848. 



'•' Derived from scoivo?, comraon, and zyjyiJ.y., propcrly somewhat that is pourcd out into sometbiiig, but 

 here ineant as an expansion or efflueucc. 



