PLUMATELLA. 127 



diffused in adhesion to the stone, which is perhaps peculiar to the growth 

 of the species ; but in some parts branches arose an inch or more, quite 

 free, bearing eight or ten hydrse. This is probably indicative of high luxu- 

 riance, requiring both time and a favourable situation. 



Lateral adhesion, however, is the nature of the zoophyte. A small 

 portion, deposited in a watch-glass, began to adhere in time. 



We have seen that the Alcyonella testifies a preference for wood, 

 or, if accidentally obtaining a position there, it vegetated luxuriantly. I 

 cannot affirm that there is a similar preference, or that similar benefit of 

 the Plumatella succeeds on its adhesion to stones, but certainly this is 

 alike favourable as any other position. 



About two miles west of the city of Edinburgh, is a pool of consider- 

 able depth, at the hamlet of Blackball, part of the possessions of the 

 Trinity Hospital, a charitable institution for the reception of aged persons. 



This pool appears to have been originally a spacious stone quarry, 

 and is always full of water, to which there is no visible outlet. Nume- 

 rous stones, reminding me much of the quality of those near Fenton 

 Tower, and of various dimensions, lie near the edge of the northern part. 



Having resorted thither many years ago, I found the under surface 

 of some of the stones invested by beautiful specimens of the Plumatella. 

 The best were brought from the south-west, which place was inaccessible 

 by myself personally. 



All the specimens were in lateral adhesion ; but I did not remark that 

 they appeared to spring from a central point. They consisted of a stem 

 with boughs and branches, diffusing more profusely from one side than 

 the other, and terminating in tubular orifices, about an eighth of an inch 

 above them, when most luxuriant. By this, I mean it to be understood, 

 the projection was vertical, or at right angles to the product, which must 

 be considered as spreading horizontally. It is difficult to render such 

 descriptions intelligible. Hydra; issued from the orifices. The general 

 tendency of vegetation may be considered as represented in Plate XXXT 1 1 . 

 figs. 1, 2. 



Specimens, of all different dimensions, but without any strict unifor- 

 mity in the arrangement of the parts, spread upon the stones. Some ex- 



