130 Scientific Proceedings, Royal Dublin Society. 



The columnar epitlaelium of the stomatodseum (oesophagus) 

 passes down the perfect mesenteries as the mesenterial filament 

 (fig. 10), where it is provided with nematocysts and gland cells. 

 H. Y. Wilson (1888) has given his reasons for concluding that 

 the mesenterial filaments in Manicina areolata are derived from 

 the ectoderm of the cesophagiis, and my sections appear to me to 

 indicate the same for Euphyllia. The filaments consist merely of 

 a single lobe, no lateral ciliated tracts being present. Everywhere 

 the ectoderm is ciliated. 



The earliest account we have of the development of a coral is 

 that of Astroides calycularis by de Lacaze-Duthiers (1873, p. 269). 

 He several times points out the essential similarity between the 

 earlier stages of this coral and those of the Actiniae, especially 

 those of Actinia equina {mesembryanthemiim) . So marked is this 

 that he says he would not be able to distinguish between some 

 hurried sketches which he made of both species if he had not 

 happened to have drawn them on different kinds of paper. On 

 p. 312 he says " the embryonic chambers ( ' lobes') follow an order 

 ('loi') identical with that which I have demonstrated for the 

 Actiniae." I have already (1889, pp. 346-350) given an abstract 

 of the latter. His account of the formation of the calcareous 

 parts does not now concern us. 



Yon Koch (1882) studied the same coral with a view to inves- 

 tigating the origin of the skeleton. He does not give a descrip- 

 tion of the order of the appearance of the mesenteries, and the 

 only point I wish to draw attention to is his discovery of promi- 

 nent endodermal ingrowths into the coelenteron of the larva 

 between the mesenteries, and into which the ectoderm subse- 

 quently invaginates to lay down the septa. 



The most complete investigation of the early stages of the 

 development of a coral is that of Manicina areolata by H. Y. 

 Wilson (1888, p. 191). The following abstract is entirely given 

 in Dr. Wilson's own words : — 



The normal segmentation which goes on in the body of the 

 parent results in the formation of a blastosphere with a very large 

 cavity. The blastophere is markedly bilateral, and is without 

 cilia. Delamination appears to be the exclusive means by which 

 the endoderm is formed. The cavity of the blastosphere having 

 been filled up by the endoderm segments a solid planula is formed. 



