142 Tlie Ameficait Geoloijist. Marcli,i895 
stitial Ijuds rortuitous. Tiistcad of being divergent, the cor- 
allites here are i)arallel and contiguous. 
In the braiieliing varieties, however, tlie growth, as deter- 
mined by mature specimens, is exclusively by interstitial 
germination. As can readih^ be seen, this, joined to a limi- 
tation in the lengtii of each corallite, would produce a trunk- 
like corallum, the l)ranching being effected by the outgrowth 
and prolongation of a number of corallites in a bod3^ There 
is no permanent apical bud, but one assumes a central position 
for a time, and then swerves outward, terminating at the 
perimeter, while another takes its place. Pf)ssibl3^ bifurcation 
of a stem may result from the deflection or divergence of two 
cells of nearly e(|ual size, having a central position. 
The hemispherical forms, therefore, seem, in their mode of 
growth, to stand midway between the explanate and the 
branching forms. These coralla have no proper limit of 
growth, and the size which they attain depends largely upon 
external physical conditions. As the ilendroid shape seems 
to be a subsequent specialization of the pyriform variety, its 
earlier development would prol)ably agree with F. forbesi, 
while both forms, the globose and the dendroid, pass through 
a more or less explanate stage. The explanate and arborescent 
varieties, however, have not been investigated by the writer 
in their earlier stages. The affinities of Favosiles as deter- 
mined by its mode of growth would seem to be with AnJopora 
and Ilouiiiujeriit rather than witii any other genera of the 
Perforata axeei^tiu^ Jfichelitu'a and Pleitrodictiiv m. 
Like rieiirodicliiinii, Farosifcs passes through an auloporoid 
stage* represented by the initial cell. When one or two sec- 
ondary cells have been added, the corallum can still be likened 
to two auloporoid cells, where, the stolon being redui-ed to a 
mere pore, the corallites themselves are hrouglit into close 
apposition. Kven a large favositoid colony can, in the same 
way, be compared with a colony of Axlopora, although in the 
latter, as far as known, so many as four cells are not budded 
from one individual. A further point of similai'ity is estab- • 
lished by the fact, that, in both genera, the individual cells 
produce buds on one side only. 
Nicholson and other writers have apparently ignored this 
*First pdintrd out by IJcccIht (I. c. ) in coiiiii'clioii wilh Pliiirddirtijuni. 
