ORDER ACTINOIDEA. 81 
existence at the developement of the young, which thus starts from it. 
In figure 33, three polyps proceed together from the centre of the 
parent; and, in 34, the new polyps sprout just exterior to the centre. 
Nothing in the history of corals seems more remarkable than this 
strange mode of reproduction. Yet the fact, that the Tubularie and 
some Sertularide, drop their flowers, and renew them at intervals, as 
explained in § 18, appears to be quite analogous. In these Cyathophyl- 
lide, the parent, at the budding period, appears to lose its tentacles 
and disk, as in the Tubularie#, which may disappear by the with- 
drawal of nutriment, needed for the new developements in progress ; 
life remains only about the centre, and from this part, the germ rises 
and the young is produced, the parent surrendering its existence at the 
birth of its successor, or soon afterward. In the second of the above 
figures, three young proceed from the ashes of the parent, instead of one. 
The third figure shows that many germs may exist and grow out from 
different parts of the summit in the same course of changes. This 
process is closely related to the interrupted mode of increase ex- 
plained in § 62. 
82. From the preceding discussions, we perceive that glomerate, 
foliaceous, and ramose forms may occur under each mode of budding 
and growth. Yet glomerate zoophytes are most common among the 
Astreacea, and here alone they assume hemispherical or globular 
shapes of perfect symmetry ; branching and foliaceous species are 
few in number in this tribe, and are distinguished by having the 
buds open a little below the apex, as well as by their lamello-striate 
surface. The Madreporacea and Caryophyllacea present occasional 
glomerate forms, usually of rude shape; but generally they are ramose, 
and often foliaceous. ‘The branches are not lamello-striate, and the 
buds open at the extreme apex or margin. The Alcyonaria may pro- 
duce branching coralla through their foot-secretions, and occasional 
segregate forms, like the T'ubipores; but none are yet known which 
are properly massive. 
Both massive, foliate, and ramose species often belong to the same 
genus, and in some instances, as before stated, a coral is thin foliaceous 
in one part, and glomerate in another, or covered with rudimentary 
branches. 
In conclusion, the principal distinctions, as to modes of growth 
among zoophytes, are as follows : 
1. Acrogenous, when polyps grow upward indefinitely, death taking 
place at a corresponding rate below; and the reverse, non-acrogenous. 
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