CORAL ZOOPHYTES. 83 
and mouth; but in many instances this does not take place till the 
young animal has proceeded from them. ‘The refuse from the food 
after digestion in the stomach is also ejected by the mouth, as this is 
the only opening to the alimentary cavity. Other excrementitious 
matters, separated on the final elaboration of the chyle and its assimi- 
lation, may escape through the sides of the animal, the openings at 
the extremities of the tentacles, or in general by whatever pores or 
passages water may be ejected in the contraction of the animal. 
One of the most singular peculiarities of polyps is their ready 
restoration of a lost part. Kven a fragment will go on to complete 
the entire animal again. As with the fabled hydra of old, the knife 
is used but to multiply, for every section becomes a new animal. 
In all the points mentioned in the description here given, the polyp 
of ordinary coral and the actinia are identical. 
b. Process of budding.—There is one mode of reproduction which, 
although having no necessary connexion with coral secretions, belongs 
almost exclusively to coral polyps. This is reproduction by buds ; and 
the process is so similar to the production of buds in vegetation, that 
a remembrance of the latter will aid much in conceiving of it. The 
bud generally commences as a slight prominence on the side of the 
parent: the prominence enlarges, and soon a circle of tentacles grows 
out, with a mouth at the centre; enlargement goes on till the young 
finally equals the parent in size. Thus by budding, a compound group 
is commenced; and it is evident that if the parent and the new polyp 
go on budding again, and so on, the compound group may continue to 
enlarge. This is the fact in nature. The polyps, one and all, continue 
propagating by buds, until in some instances thousands, or hundreds 
of thousands, have proceeded from a single one, and the colony has 
spread toa large size. Such are the Madrepora and Astrea. ‘There are 
modifications of this process, analogous to those in vegetation, but we 
need not dwell upon them in this place. 
It is obvious that the connexion of the polyps in such a compound 
group must be of the most intimate kind. The several polyps have 
separate mouths and tentacles, and separate stomachs; but beyond 
this, there is no individual property. ‘They coalesce, or are one, by 
intervening tissues, and there is a free circulation of fluids through 
the many pores or lacunes. The zoophyte is like a living sheet of 
animal matter, fed and nourished by numerous mouths and as many 
stomachs. In some species the coalescence is confined to the lower half 
of the polyps, or to a still less part; and in this case the animals pro- 
ject above the general living surface. Polyps thus clustered, spreading 
