260 Mr. H. J. Carter on the 



What part, then, did the " stellate venation" perform? and 

 is there any thing analogous to it in the organisms just men- 

 tioned ? 



From what has been stated of the stellate venation, it does 

 not appear that it had an external opening in the fresh state, 

 as will be shown hereafter, whether with or without a central 

 cell or inflation, such as that, in the latter instance, figured by 

 Baron Rosen (op. et I. c.) — and therefore that its functions were 

 not excretory like those of the canal-systems of sponges, which, 

 possessing a stellate form like that of the stellate venation of 

 Stromatopora, are present on the surface of some species. 

 Again, the stellate venation in Stromatopora appears in every 

 layer however thin, which, in some specimens of the recti- 

 linear species from the Pit-Park Quarry at Dartington, split 

 off individually, each bearing its own centres of stellate vena- 

 tion, which are generally situated one over another as they 

 are on the summits of the gentle elevations which charac- 

 terize the growth of the species. This, too, is not like the cha- 

 racter of the stelliform excretory canal-systems of sponges, 

 which are confined to the surface of the few species that pre- 

 sent them. We therefore, however like the latter may be to 

 the stellate venations of Stromatopora, may dismiss this specu- 

 lation from our conjecture. 



Next, as to any thing like the stellate venation in any of 

 the recent or fossil specimens of organisms apparently allied 

 to Stromatopora. 



Here we must first advert to what takes place in the deve- 

 lopment of the polypary of Hydractinia echinata and H. cal- 

 carea respectively, all of which may be found detailed and 

 illustrated in extenso in my communications on the subject 

 published in the ' Annals ' (vol. xi. p. 1 &c. pi. i., 1873 ; 

 and vol. xix. p. 46 &c. pi. viii., 1877), but which will be 

 briefly repeated here for our present purpose — that is, to show 

 that there is a grooved venation in dried specimens of the 

 recent species to which I have alluded, previously formed by, 

 and afterwards supporting in the living state, a stoloniferous 

 branched tubulation whose office is similar to that of the 

 hydrorhiza of the Hydroid Zoophytes, viz. to produce the 

 rudiments upon which the whole of the rest of the polypary 

 is erected. This tubulation may be first observed in the pro- 

 liferous membrane of Hydractinia echinata, as well as in that 

 of H calcarea, and is easily recognized by the presence of 

 horny or calcareous points, as the case may be, upon its ex- 

 ternal surface, which are not only the rudiments of the poly- 

 pary, but those of the grooved venation, as before stated, in 



