MATTHAI— RECENT COLONIAL ASTR^ID^ 29 



blast of vertebrates, hence his use of "ectodermal" and " endodermal " was "merely for 

 convenience and not as expressing a definite homology" (100, p. 271). 



Gardiner in 1899, from a histological study of the filaments of Ccenopsammia, also 

 came to the conclusion that they were entirely ectodermal structures, and supported 

 H. V. Wilson's contention based on embryological data ; he added further that " the 

 lateral parts of the mesenterial filaments are similar in structure to the ' Flimmerstreifen ' 

 of the Hertwigs and have apparently the same function" (49, p. 375). Duerden, from 

 his study of West Indian Madreporarian polyps, inferred that their filaments were 

 entirely endodermal, the histological resemblance between them and the stomodseal 

 ectoderm being a secondary feature. His reasons for this view were that filaments were 

 present on incomplete mesenteries which never reached the stomodeeum, that the reflected 

 stomodeeal ectoderm could not be traced up to the oral-disc and thence to the free edges 

 of the incomplete mesenteries, that in the upper regions of the latter filaments were absent 

 or incipient while they were well developed below, that filaments appeared independently 

 on some of the primary mesenteries before the latter reached the stomodseum. Duerden 

 regarded the " reflected ectoderm " as " the stomodseal ectoderm passing along the 

 mesentery to establish structural continuity with the upwardly growing filament " 

 (p. 479). 



The appearances in my sections favour the view of the ectodermal nature of coral 

 filaments held by H. V. Wilson and Gardiner. In Cyphastrea chalcidicum (Forsk.) 

 I have found traces of the upwardly reflected stomodeeal ectoderm as far as the oral-disc ; 

 perhaps this ectoderm might be continued to the secondary mesenteries and finally course 

 down their free margins as their filaments. Of course, questions like these could be 

 settled only by a study of the development of coral larvae*. 



Acontia and cinclides. Conflicting accounts have been given by different authors 

 with regard to the presence or absence of these organs in coral polyps. Fowler in 1884 

 and Bourne in 1887 at first applied the term acontia to the prolongations of the 

 mesenterial margins in Flahellum and Fungia respectively, and found them capable of 

 being protruded through permanent openings (cinclides) in the oral-disc, the former author 

 regarding " the contorted mesenterial filaments " of Moseley as identical with the acontia 

 of Gosse ; Bourne in 1888 withdrew his application of the term "acontia" to these 

 prolongations. H. V. V\7'ilson could find no free acontia in Manicina, but noticed that 

 the filaments which were attached along their whole length to the mesenteries could be 

 extruded through the mouth and through pores in the body-wall. With regard to 

 Ccenopsammm, Gardiner remarked that "the filaments are attached to the mesenteries 

 for their whole length, and are without free portions (acontia) at their lower ends" 

 (p. 367), whereas in the Turbinolids he examined in 1904 "the lower ends of the filaments 



* Referring to the probable formation of the stomodasum in Flahellum, Gardiner says, " The only logical 

 method of conceiving the formation of the stomodseum of the adult to take place is to suppose that the external 

 body-wall grows inwards catching up the edges of the mesenteries in its progress. It finally reaches the 

 mesenterial filaments, which by fusion together, assisted by the down-growth of the body-wall form the 

 stomodseum" (p. 151). My examination of Gardiner's "young polyp" of Flahellum (figs. 3 and 4) confirms 

 the facts on which his conclusions are based, viz. that it had no trace of tentacles or stomodieum and that 

 filaments were present on the margins of the mesenteries. 



