149 



are merely formed by the fusion across the axial fossa of the 

 body-wall, covering the septal edges, and may arise in any 

 corallite of any genus. The origin of rootlets has been 

 clearly shown by Lacaze Duthiers* in F. anthophyllum. 

 They seem to arise as a flowing over the edge of the cup of 

 the tissues of its polyp, probably brought about by the 

 absence of favourable circumstances for the deposition of the 

 skeleton and the presence of more suitable conditions for the 

 increase of the polyp itself These considerations lead to the 

 absorption of the genus Rhizotrochus^ while the close resem- 

 blance between the buds of B lastotrochiis and Flabellum 

 scarcely allow of their being distinct genera. 



The comparison of the anatomy of the polyps of F. pcwoni- 

 nuin and F. rubrum show that they are separated 

 by the fact that all the septa in the former are ento- 

 coelic and have tentacles over them, whereas half the septa 

 of the latter are exocoelic, with no correspondingly situated 

 tentacles. The mesenteries of the former are hence twice as 

 numerous as the septa, and of the latter the same in number. 



Moseley's accountf of the anatomy of the genus is rather 

 confused. A generalised transverse section, Moseley's fig. 

 lo shows twice as many mesenteries as there are septa 

 in the genus, and it is stated that there are the same 

 number of tentacles as there are septa. This, as a 

 generic character, is contradicted by the same author's 

 fig. 12 of F. japoniciuii, which shows 48 tentacles 

 corresponding to septal cycles I. — IV., while cycle V. is 

 also stated to be present. From this figure the presumption 

 is that the septa and mesenteries alternate in this species as 

 in F. rubrum. A figure of a longitudinal section of F. ala- 

 bastrum shows three orders of mesenteries, attached (1) to 

 the lower edge of the stomodoeum, (2) to the junction of 

 stomodoeum and peristome, and (3) to the peristome near 

 the bases of the tentacles, an arrangement similar to that 

 found in both F. rubrum and F. pavoninum. The ova occur 

 on all the mesenteries according to size, but are not repre- 

 sented in any determinate series, being scattered all over the 

 lower parts of the mesenteries. 



In F. anthophyllum, according to Lacaze Duthiers [Joe. cit.), 

 the tentacles and septa correspond in number. The mesen- 

 teries likewise are of the same number, and the arrangement 

 accordingly is such that half the septa and tentacles are exo- 

 coelic. The testes consist of polyhedral masses, and the 

 ovaries each of 4-5 ova placed in a row, a similar arrange- 

 ment to F. rubrum. 



* " Evolution dii Polypier du Flabellum anthophyllum," Arek. de Zool. txp. 

 It gen., 3e ser, t II., p. 445 et eeq. (1894). 



t Challenger Report on Corals, pp. 162-4, pi. xvi., figs. 10-12 (1882). 

 A2754. P 



