ZoophyUs. 279 



enclosed by the subsequent growth of the same animal." This does 

 not appear to be the true explanation. In the case of the globular 

 protuberances mentioned before, it is formed by, or beneath, the in- 

 vesting membrane of the axis, while the fleshy bark remains entire ; 

 and the repetition of these spots in the bend of the branches pre- 

 cludes the idea of such a fortuitous enclosure. The opinion of Ellis 

 appears, therefore, to be erroneous, but is rather an error of deduc- 

 tion than of observation. Near the root the axis is frequently studded 

 with small cavities, some of which are empty, while others are more 

 or less filled with this greyish matter ; the most inferior are generally 

 empty, while in the more recent it is more or less abundant. From the 

 gradation of quantity observed in these cavities, it seems reasonable 

 to suppose that each had formerly been occupied by this grey matter, 

 which, in some way or other, had been since removed. There appear 

 to be only two methods in which such a removal could occur ; either 

 from degeneration or absorption. It is exceedingly rare to observe 

 any marks of degeneration, either in the form of powder or a disor- 

 ganized appearance of the substance itself, and therefore it seems 

 most probable that its removal depends upon absorption. 



The pith is white, and runs through the centre of the trunk and 

 branches, and is smaller in the lower and older than in the upper and 

 newer portions. In a transverse section of recently formed parts, it 

 is found to be composed of irregular- sized cells, quincuncially ar- 

 ranged ; in a longitudinal section, to be formed of cells similar in 

 shape to those observed in the fleshy bark, but smaller in size. In 

 the older portions of the pith this cellular structure cannot be ob- 

 served. From the pith being smaller in the older than in the younger 

 parts, the cells are most probably obliterated by pressure, either be- 

 coming ruptured, or so closely compacted that their ultimate structure 

 cannot be detected, even by maceration. This pith differs in several 

 important particulars from the pith of vegetables. In vegetables it 

 is continuous from the trunk through all the branches ; in the Gorgo- 

 nia verrucosa it is divided into numerous small compartments by 

 transverse horny septa, and the pith of the branches is separated 

 from the pith of the trunk by several layers of the fibres of the axis, 

 in such a manner as to have no immediate communication with each 

 other. This has been noticed and figured by Ellis and others. The 

 pith of vegetables is also surrounded by ducts and tracheae, which I 

 have never detected in the Gorgonia ; hence there are several im- 

 portant discrepancies between them. 



The pith acts an important part in the formation of new branches, 



