70 ZOOPHYTES. 
the branches have no one polyp at apex more prominent than the 
others. In the Madrepores, a spiral arrangement of the polyps may 
sometimes be distinguished, resulting from some 
regularity in the developement of buds, in turn, 
from the different sides of a parent-polyp. 
72. A periodicity in the budding process is 
well illustrated in the jointed corals of the Gor- 
gonia family. The Meliteas form foot and 
tissue secretions, like the true Gorgonie ; but, 
instead of having the former as an axis, within 
the others, the two appear to constitute alter- 
nating joints. This may be accounted for by 
supposing the budding to be periodical at the 
; apex of the branch, the new buds adding to the 
extremity, first, their foot-secretions, and then 
their tissue-secretions. 
Fig. 31. 
73. It is obvious that the form and position of 
the growing stems must also depend on the sym- 
metrical or unsymmetrical production of buds. 
The stem will be cylindrical when the buds are 
equal and open alike in every direction. If they 
form only in two opposite directions, in a single 
Dendeony iia. series, we have a zoophyte with two-edged 
branches, as in some Pterogorgie.* Or if the buds opening in two 
directions spread sidewise, instead of forming a simple vertical series, 
the zoophyte produced is an erect plate, with polyps opening on the 
opposite surfaces, as in some Millepore. 
When the budding is unsymmetrical, the zoophytes formed are 
oblique or horizontal. The buds, having an oblique tendency, may 
pass off at a different angle on opposite sides, or elongate more rapidly 
on one side than the other, or they may be confined to one side alone. 
Cylindrical stems, in consequence of this oblique or unsymmetrical 
mode of budding, become horizontal, as in many Madrepores; the 
buds open equally in every direction, but elongate most rapidly on 
one side of the branch in a horizontal direction. By this mode of 
increase, the vase Madrepores are produced,} some of which are several 
feet in diameter. 
A few remarks may be added upon the mode of branching in these 
* The Gorgonia anceps and other species with seriate polyps. + See plates 32 and 33. 
