Natural History of British Zoophytes. 323 



whole animal, there is not merely an upward growth, but creeping- 

 tubes, " full of the same living medullary substance with the rest of 

 the body," are projected from the base along the surface of the object 

 of fixture. " These tubes not only secure it from the motion of the 

 waves, but likewise from these rise other young- animals or coraUines, 

 which growing up like the former, with their proper heads or organs 

 to procure food, send out other adhering tubes from below, with a 

 further increase of these many-headed branched animals ; so that in 

 a short time a whole grove of vesicular corallines is formed, as we 

 find them on oysters, and other shell- fish, when we drag for them in 

 deep water."* 



There are many facts which prove that the growth of these poly- 

 pidoms is very rapid, but not more so than might be anticipated when 

 it is remembered how vast is the number of polype architects ; and 

 no sooner is a new branch extended than it becomes almost simul- 

 taneously a support of new workers which, with " toil unwearyable," 

 add incessantly to the materials of increase. Their duration is vari- 

 ous : some have only a summer's existence, as Campanularia genicu- 

 lata ; many are probably annual, and the epiphyllous kinds cannot at 

 most prolong their term beyond that of the weed on which they 

 grow ; but such as attach themselves to rocks are probably less pe- 

 rishable, for their size and consistency seem to indicate a greater age : 

 it is thus with the Tubularise and some of the compound Sertulariadse. 



But the life of the polypes considered abstractedly is probably in 

 no instance coetaneous with the duration of the polypidom. for the 

 lower parts of this become, after a time, empty of pulp and lifeless, 

 and lose the cells inhabited by the polypes, which, in an old speci- 

 men, are to be found in a state of activity only near the summit, or 

 on the new shoots. The Thuiaria thuja affords a remarkable example 

 of this fact ; the branches which carry the polypes dropping- off in 

 regular succession as younger ones are successively formed, so that 

 the polypidom retains, throughout its whole growth, the appearance 

 of a bottle brush, the naked stem and the branched top being kept in 

 every stage in a due proportion to each other. Sertularia argentea, 

 Plumularia falcata, &c. are subjected to the same law, — the primary 

 polypiferous shoots being- deciduous, so that in them also the stalk 

 becomes bare, while the upper parts are graced with a luxuriant rami- 

 fication loaded with tiny architects. But in our eagerness to genera- 

 lize, let us not forget that there are some species, as Sertularia pumila, 

 abietina, &c., in which this process of successive denudation is not ob- 

 servable, perhaps, however, because of their form, which is not of a 



* Ellis and Solander's Zoophytes, p. 33. 



