68 ZOOPHYTES. 
arrangement of the polyps around the branch, especially apparent at 
the apex. ‘The spire, in some species, goes around by the right, and, 
in others, by the left; and a single circuit of the spire appears to 
contain five polyps, though with some irregularity. In figure 31, 
this mode of arrangement is seen in an end view of a branch enlarged. 
The calicles are numbered, to show their relative positions, com- 
mencing with the apical as number 1. At the same time that the 
figures exhibit the spiral order, they also indicate the fact stated, that 
there is some irregularity in this arrangement. 
2. Lateral budding, with acrogenous growth, in the polyps. 
68. When polyps have the upward mode of growth, different forms 
result, according as the budding power is general throughout the zoo- 
phyte, or belongs only to a limited number of polyps,—the older 
individuals losing the power by age. 
69. Unlimited symmetrical budding. If each polyp, as soon as pro- 
duced, buds like the parent, and retains this power indefinitely, or 
without limit, the zoophyte will necessarily take on globular or 
hemispherical forms ; for increase, in such a case, takes place equally 
in every direction. There are certain species among the massive 
Porites, in which these forms thus result. Yet, owing to a slight 
irregularity, or the more rapid developement of buds in some parts 
than others, these zoophytes have generally a form irregularly glome- 
rate, rather than symmetrically globular. 
Globular or hemispherical forms are produced in the same manner 
among the segregate, as the massive or aggregate zoophytes. ‘The 
Columnarie are examples of species consisting of adnate prisms. In 
the Tubipores, the polyps form, by their secretions, parallel tubes, 
which, as they grow and give out buds from their sides, necessarily 
diverge a little, and a convex or hemispherical form is the result. 
The tubes are united at intervals by transverse plates, which are 
formed at the budding process, as is apparent from the fact that the 
buds proceed from these plates; and the internal cavity may be 
traced into them, though very much reduced in size. ‘The process of 
budding is similar to that of the Aulopora, except that the polyps 
have an acrogenous growth, and bud periodically as they grow up- 
ward; and, moreover, the buds, at the time they are given out, 
coalesce laterally into a plate, like the Xeni, instead of forming a 
network : after this coalescence, they lengthen upward between the 
other polyps, and thus add new tubes to this “organ-pipe” coral- 
zoophyte. 
