GENERA OF FAVOSITID^. 147 



of the coralliim, and havinof the coralHtes radiatlnor from it on 

 all sides. None of the American examples referred to this 

 species by Meek and Worthen {loc, cit.) show any traces of 

 this structure. The nature of this curious body has been much 

 disputed, but it has generally been regarded as being one of 

 two things — viz., either the cast of the burrow of some boring 

 Annelide which mined the coral after the latter had attained 

 its full growth, or else the calcareous tube of some Annelidous 

 genus like the existing Serpzda, to which the coral attached 

 itself when young, and which it subsequently enveloped in the 

 process of development. This latter view, which would make 

 the phenomenon an instance of " commensalism," is the one 

 which was adopted by Edwards and Haime, and in which they 

 have been followed by most subsequent writers. It is a note- 

 worthy fact, however, that a tube of precisely the same nature 

 has been found by me to exist in the only specimens of P. sty- 

 lopJwrum, Eaton, which I have been able to section for the 

 microscope ; and though I do not pretend to offer any satis- 

 factory explanation as to its true significance, I have been able 

 to satisfy myself of the following points, which have a consider- 

 able bearing upon any view which may be framed upon this 

 subject : — 



1. The mere fact of the occurrence of this peculiar structure 

 in two different species of the same genus, in regions as widely 

 remote as Europe and North America, is prima facie, though 

 by no means conclusive, evidence against the view that the 

 " vermiform body " is merely the work of a parasite, or is the 

 tube of an Annelide upon which the corallum grew. 



2. The " vermiform body " in P. stylophormn, Eaton, either 

 existed before the coral, or grew simultaneously with it. This 

 is shown incontrovertibly by the fact that, in sections, the coral- 

 Htes are seen to accommodate their shape to that of the t7t.be, and 

 to be fixed to it in places by their bases. In no instance ob- 

 served by me does the tube cut across the corallites (see 

 PI. VIII., figs. I - I b, where the tube is shown in section). 

 This observation is sufficient to conclusively negative the view 



