499 
of Edinburgh, Session 1874-75. 
a. Simple calicular gemmation , in which the corallum sends up 
from its calicine disc a single bud, which usually repeats the pro- 
cess, until there is produced a succession of corallites vertically 
superimposed upon one another. The peculiarity of this process 
consists in the fact that the same calice never produces more than 
one bud. 
b. Compound calicular gemmation , in which the primitive coral- 
lite throws up two or more buds from its oral disc, these in turn 
usually repeating the process, till the corallum comes to form an 
inverted pyramidal mass, composed of numerous corallites diverging 
from the base. 
c. Basal or marginal gemmation , in which new corallites are pro- 
duced at the circumference of the colony or along certain definite 
lines proceeding from the base. 
d. Parietal or lateral gemmation , in which the increase of the 
corallum is by the production of buds at gome point in the walls of 
the parent corallite between the lip of the calice and the base. 
e. Fission , in which the growth of the corallum is effected by 
the cleavage of the calice of the original corallite or corallites. 
Numerous examples were adduced of the occurrence of the 
above modes of growth, singly or in combination, amongst the 
Palseozoic corals, and various modifications of these processes were 
discussed. 
The author next discussed the value of the mode of growth of 
the corallum as applied to the classification of the Paleeozic corals, 
and arrived at the conclusion that much stress could not be laid 
upon this point unless accompanied by other distinctive characters 
as well. The chief grounds upon which this conclusion was based 
were, that allied forms in the same genus, and sometimes even 
different individuals in the same species, show entirely different 
modes of growth ; that forms belonging to the most remotely allied 
groups often increase in the same way; and finally, that the diffi- 
culty in determining the precise mode of growth amongst some of 
the fossil corals is so great as often to render this test practically 
inapplicable. 
In conclusion, the author discussed the relations between the 
growth of the different parts which may comprise a compound 
corallum, as regulating its final form and structure. 
