'SO 



In his description of F. paiaoo}iic)ium Fowler* has woefully 

 confused theca and epitheca, and septal trabeculae with 

 columella. There are 4 orders of septa, all entocoelic and 

 with tentacles. Mesenteries I. and II. (on either side of 

 septa I. and II.) are alone attached to the stomodoeum, while 

 in F. riihriDU and F. pavoninnm I. -III. are so attached. The 

 stomodoeum is stated to have well marked gonidial grooves 

 and " Through periphery of mouth-disc (peristome) protrude 

 the acontia " through " definite openings." t 



The above short resume of our present knowledge of the 

 anatomy of the polyps shows that the differences in the 

 corallites are correlated with differences in the polyps. For a 

 thoroughly scientific classification a knowledge of the polyp 

 anatomy is essential. In the caseof /". ruhriiDi it confirms the 

 diagnosis of the species and its variations, which was first 

 studied on the dried coralla alone. If there is so much 

 specific variability in the polyps of one genus as implied by 

 the above, why not in all genera. Of the specifically 

 variable polyp characters 1 would only draw further attention 

 to the number of mesenteries meeting the stomodoeum and 

 depending from it. My experience in F. rubrum is that this 

 character is much less variable than any founded on 

 numbers of septa of different sizes, etc. Indeed, it seems to 

 me to be probably one likely to be of no inconsiderable 

 value for separating our species from one another. 



The importance of the development of the corallite lies in 

 the fact that the regular 6-system radial arrangement of 

 septa is found dominating the early stages, whereas with 

 growth the calicle becomes elongated, bilaterally symmetrical 

 with 20 — 24 equal septa. However the mesenteries may 

 develop, the septa in all genera of Madreporaria support 

 Milne-Edwards and Haime's views on radial symmetry 

 being primitive in the group ; that in ejEfect the group was 

 evolved from forms with pronounced radial symmetry. 



The minute anatomy in different polyps varies enormously 

 in accordance with the state of the polyp so far as feeding is 

 concerned. In one polyp I found large numbers of a Forami- 

 niferan, which Mr. J. J. Lister has referred to the genus 



* "The Anatomy of the Madreporaria," Quart. Jtur. Micro. Set., vol. XXV., 

 p. 577. pi. XL. (1S85.) 



t Fowler's deacription of anatomical details is meagre and the figu.tB are 

 diagrammatical. According to Fowier's account there nre a few points of 

 difference from F. ruhrum. The mesenterial filaments ura naid to be found ou ilie 

 whole frea edges of the mesenteries, even below where the ova are situated aud the 

 acontia given i-ff. The oblique exccoelic muscles of the mesenteries — presumably 

 traverniiig the structureless lamella — become (according to Fowler) the external 

 longitudinal coat of the tentacles, and the longitudinal muscles oi the mesenteries 

 the circular fibies of the same. The acontia are said to be set with both tentacular 

 and mesenterial nematocysts, while Fowler's figure of the stction of one is peculiar 

 in only showing a single thread-cell. 



