88 
ZOOPHYTA HYDROXDA. 
ceived from an external source, and circulating through the 
whole animal, there is not merely an upward growth, but creep- 
ing 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* 44 These tubes not only secure 
it from the motion of the waves, but likewise from these rise 
other young animals or corallines, 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 
polypidoms is very rapid, but not more so than might be anti- 
cipated when it is remembered how vast is the number of polype 
architects ; and no sooner is a new branch extended than it be- 
comes almost simultaneously a support of new workers which, 
with 44 toil unwearyable,” add incessantly to the materials of in- 
crease. Their duration is various : some have only a summer’s 
existence, as Campanularia geniculata ; many are probably an- 
nual, 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 perishable, for 
their size and consistency seem to indicate a greater age : it is 
thus with the Tubularise and some of the compound Sertu- 
lariadse. 
But the life of the polypes considered abstractedly is proba- 
bly in no instance coetaneous with the duration of the polypi- 
dom, for the lower parts of this become, after a time, empty of 
pulp and lifeless, and lose the cells inhabited by the polypes, 
* Ellis and Solander’s Zoophytes, p. 83. 
“ New buds and bulbs the living fibre shoots 
“ On lengthening branches, and protruding roots ; 
“ Or on the father’s side from bursting glands 
“ The adhering young its nascent form expands ; 
“ In branching lines the parent-trunk adorns, 
il And parts ere long like plumage, hairs, or horns.” 
Darwin’s Temple of Nature , Canto ii. 
4 
