Mr. H. J. Carter on the Strom atoporidge. 305 



that the ultimate radicles of the branches of the different j^a 

 unite with each other, and thus the structure is extended. 



This, which may be termed the " proliferous membrane," 

 hydrophyton of Allman, or coenosarc, may be assumed to have 

 existed in all Hydrozoic coenenchymata of the kind, whether 

 present or past; and thus our knowledge of the recent structure 

 will be found to afford us decisive explanation of that which 

 might otherwise have remained conjectural for an unlimited 

 period. 



Passing on to Millepora alcicornis^ whicli is a Hydrozoic 

 coral, we find precisely the same kind of grooved venation, 

 indicative of the previous existence of a "proliferous mem- 

 brane," as in Htjdractinia echinata^ only that, for the most 

 part, it is concealed by the surface-layer, which requires to be 

 picked off with a sharp-pointed instrmnent to bring the venation 

 into view. (Scraping off the layer with a sharp knife will also 

 do this, but not so satisfactorily, especially as by the former 

 method portions of the dried vessels themselves often remain 

 in situ.) Yet occasionally the grooved venation appears in 

 the surface, as may be seen on a sj^ecimen at the British 

 Museum in one of the upright cases in tlie coral-room, 

 labelled accordingly. (This specimen is composed of cylin- 

 drical anastomosing branches beset with short, stout, spine-like 

 processes, altogether presenting a flat clathrous mass about 

 twelve inches broad and nine inches high as it now stands.) 

 There is also another specimen, more like the typical Mille- 

 pora alciconiis in shape, from the flatness of its branches, 

 whereon the grooved venation is partial — that is, obvious out- 

 side in some parts only. This venation was seen by Mr. H. 

 N. Moseley " on the surface of a corallum in a species of 

 Millepora obtained at Zamboangan, Philippines " (Phil. 

 Trans. 1877, vol. clxvii. p. 125) ; and a similar reticulation 

 may be observed with a common lens i7i the horizontal lamina 

 of TuhijJora musica^ as it appears through the upper layer. 



In a vertical fracture of a branch of Millepora alcicornisj 

 holes here and there, indicative of the larger branches of the 

 grooved venation, may be seen just under the surface- layer, 

 while the smaller ones which rise into it are lost by becoming 

 continuous with the vermicular interspaces of thecoenenchyma ; 

 except in some instances, where the vessels which occupy 

 them appear to have become calcified and thus rendered 

 visible by a slight portion of the surface-layer being shaven 

 off with a very sharp knife. Indeed the same condition 

 sometimes leads to their permanency on the outside of the 

 surface-layer, where they may be seen with the naked eye, or 

 at least with a lens of moderate power. At the same time, 

 Ann. & Mag. N. Hist. Ser. 5. Vol. ii. 21 



