102 GEORGE MATTHAI 



narcotized in a partly expanded condition in weak solutions 

 of magnesium sulphate before fixation in formalin. They were 

 then brought up to 75 per cent, alcohol for preservation. The 

 decalcification was done in 2-3 per cent, solutions of nitric 

 acid in 75 per cent, alcohol, some of the colonies with hard 

 coralla taking as long as three months to decalcify, but, as 

 a rule, the histological condition of the soft parts has not been 

 affected to any extent by the process. 



Various staining methods were employed, chiefly Haiden- 

 hain's iron-haematoxylin followed by eosin, aniline blue, and 

 orange G (Mallory), safranin 0, borax-carmine followed by 

 picro-nigrosin and picric aniline blue. Well-preserved polyps 

 were subjected to teasing before and after maceration in the 

 Hertwig's osmic-acetic solution ; while at the American 

 Biological stations a similar investigation of fresh coral tissue 

 could not be made to my satisfaction owing to pressure of 

 other w^ork, though it was found that the method of teasing 

 was not so suited as that of serial sectioning to reveal the true 

 histological relationships of lowly differentiated tissues like 

 those of the M a d r e p o r a r i a . 



I have to thank the Governing Body of Emmanuel College 

 for financial aid in connexion with this research. 



The soft parts of the Madreporaria consist of an outer 

 and inner protoplasmic sheet and an intermediate supporting 

 lamina. The two former are described in this paper under 

 the widely accepted terms Ectoderm and En do derm, 

 which had originally been employed by Allman in 1853 to 

 denote the outer and inner layers of the Tubulariadae 

 (1, p. 368). But I have refrained from applying any of the 

 suggested names to the middle lamina since (as will be shown 

 in the course of this study), from its nature and formation, 

 this lamina does not appear to be essentially different from 

 the M e s d e r m of the T r i p 1 o b 1 a s t i c a . It may also be 

 stated at once that these laminae in Astraeid corals are not 

 discrete layers, as has been the prevalent view, but are of the 

 nature of three strata in a continuous multinucleated sheet. 



