238 PROFESSOR NICHOLSON ON THE MODE OF GROWTH AND INCREASE 
uncommon in certain of the Paleozoic corals, and gives rise to exceedingly 
well-marked results. In what is usually understood by calicular gemmation, the 
oral disc of the primitive polype produces two or more buds; these in turn 
repeat the process, and ultimately we have a mass of an inverted pyramidal] 
shape, composed of numerous corallites diverging from the base. In the 
particular mode of growth to which I propose to apply the term of “ simple” 
calicular gemmation, there is a well-marked modification of the above. The 
corallum, originally simple, after growing to a certain extent, sends up from its ~ 
oral disc a single bud. The primitive calice may or may not’be more or less 
completely obliterated by the gradual growth and extension of the epitheca 
over it; and the secondary bud may or may not produce a tertiary bud in the 
same manner as that in which it was itself produced. In any case, the mode 
of increase is by the production of s¢mgle buds from the calicine disc, and, con- 
sequently, the resulting form of the corallum is in all cases altogether different 
to what is seen in the ordinary method of calicular gemmation. 
I have, so far, only observed simple calicular gemmation in certain of the 
Cyathophyllide and Cystiphyllide, and it differs in different cases as to the extent 
to which it is carried. In Cystiphyllum squamosum, Nich., from the Devonian 
of Ohio, the primitive corallite seems never to produce more than one bud. 
This is developed from near the centre of the primitive calice, and has a direc 
tion more or less perpendicular to the plane of the old calice (or to the axis of 
the old corallite, with which the plane of the calice nearly coincides). In Cysti- 
phyllum Ohioense, Nich., also from the Devonian of Ohio, most individuals of 
the species are simple. Others, however, throw up a single bud from the 
centre or one side of the primitive calice ; but this bud, instead of being more ~ 
or less perpendicular to the axis of the coral, as it is in C. sguamosum, is usually 
continued in the direction of the original corallite. In Cystiphyllum vesicu- 
losum, Goldfuss, again, the process of calicular gemmation is carried much 
further than in the two preceding forms. When the corallum in this species 
has attained a certain growth, it commonly, though not invariably, sends 
up a new bud from some point in the calice, generally directly above the 
old one; and this, too, continues to grow for a certain period. <A third bud 
may then be produced in a like manner, and a fourth, fifth, or sixth may be 
similarly generated, until the aged corallum may consist of a series of short 
turbinate cups or inverted cones, superimposed one upon the other, the younger 
upon the older. Ina general way, the successively produced corallites conform 
more or less in direction with the primitive one; but this is by no means univer- 
sally the case, and the resulting form of the entire corallum is thus often very 
irregular and peculiar. The old cups are usually quite distinct; but they 
may be more or less completely obliterated by the gradual growth and extension 
of the epitheca over them. In these cases it becomes sometimes difficult to 
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