140 The American Geologist. Marcli, 1895 
throu^-liout the coralline is apparent, while the mechanical 
cause and geometric necessity are e(iiially obvious. It may 
be that the hexagonal symmetry (in sei)ta and buds) ol" the 
individual in a favositoid colony is due to the hexagonal form, 
together with the habit of prolific budding in the earlier 
stages, especially in the ancestral type suggested in this paper. 
The constitution of the corallum is such as to force the buds 
of each individual to fall into (5 or 6x vertical rows, and this 
in turn might aHect the development of septa. On the other 
hancf, it may be objected that for the same reason Jiexagonal 
symmetry must prevail in colonies of rugose corals, whereas 
tetrameral symmetry is found to be the rule. Among the 
Btigosd, however, budding is either calycinal, where the life 
of the parent is terminated by the act of gemmation, or, when 
lateral, is not usually prolific. 
In Fdvo.sifes one of the most noticeable features of the co- 
rallites is the mural pores, which extend in one or more verti- 
cal rows along each face, and, apparent]}', served to connect 
the visceral cavities of adjacent polyps. If a marginal row 
be observed it will be found to run parallel with the edge for 
a short distance, then, approaching it, to pass to the other 
side. There is usually an enlarged pore ujjon the angle from 
which a bud is produced, truncating in its growth the edge 
of the |)risra.* For a short distance, the original row remains 
solitarj'' upon the new face, when suddenly one or nuire rows 
are initiated, apparently bj' the young bud. In other words, 
the pores extend upward in parallel series, in an irregular and 
extended spiral. The bend in the line of pores apparently 
indicates a slight twisting on the part of the corallites, which 
may be due to the tension of the bud in its effort to acquire 
an upright position. To this cause is very likely due the in- 
termediate and alternating position of all the young cells. It 
woidd thus follow that the calcified and consequently' immov- 
able portion of the corallite did not extend as high as the 
liinge-point of the pore line when the bud was given off. It 
is not supposed that the spiral movement of the pores was 
produced by a continued and slow revolution of the corallite. 
The introduction of new series with new buds and the disap- 
*l>t'('chcr. ISOl. 'I'l-Jtiis. Coiiii. Acad., vol. \ ni. p. 2\'k <'\. sc(|. 
