PLUMES OP CEPHALODISCUS. 249 



author also directs attention ^ to a still more remarkable 

 similarity between the processes of the lophophore and the 

 lower lip of the Sipunculoid Phymosoma, described by 

 Shipley," and the plume-axes and post-oral lamella of 

 Cephalodiscus. The ends of the lower lip of Phymosoma 

 are continuous with the ends of the series of finger-like pro- 

 cesses of the lophophore, and Shipley's figure 32 on Plate 4 

 of his paper bears a close similarity to my text-figure 8. It 

 may bo not without significance that, when viewed from the 

 front, the nephridiopores of Phoronis and of Phymosoma 

 occupy the same positions with regard to the anus and other 

 parts as do the gonadial apertures of Cephalodiscus. 



While the position of the epistome of Phoronis does not 

 militate against the view here favoured of an affinity between 

 Phoronis and Cephalodiscus, it is to be noted that, 

 according to the observations of de Selys Longchamps,^ the 

 pre-oral lobe of the larva Actinotrocha^ which is homologous 

 with the proboscis of Balanoglossus and the buccal shield 

 of Cephalodiscus, disappears during the metamorphosis, 

 and does not persist as the epistome of the adult Phoronis. 



Although the occurrence of the five divisions of the ccelom 

 in Actinotrocha, corresponding with the proboscis cavity, 

 two collar cavities and two trunk cavities, claimed by 

 Masterman,^ has been contested by Goodrich,^ Ikeda,^ and 

 de Selys Longchamps,^ these last three writers agree that 

 there is a division of the ccelom into a pre-septal and a post- 

 septal part, the septum in question following the course of 

 the tentacles of the larva. It is still possible, therefore, that 



1 L. c, p. 119. 



- ' Quart. Journ. Mic. Sci.,' vol. 31, 1890, figs. 1 aud 2. 



* " Developpemeut Postembryonnaire efc Affiaites des Phoronis," 'Mem. 

 Classe Sci. Acad. Roy. Belgique,' i, 1904, p. 73. 



* 'Proc. Roy. Soc. Edinb.,' vol. xxi, 1896, pp. 62, 63, and 130; also 

 ' Quart. Jouru. Mic. Sci.,' vol. 43, 1900, p. 395. 



5 'Quart. Journ. Mic. Sci.,' vol. 47, 1904, p. 111. 



^ 'Journ. Coll. Sci. Imp. Univ. Tokyo,' xiii, part 4, 1901, pp. 540 et seq. 



^ Loc. cit., pp. 15, 16. 



