GENERAL REMARKS. 19 
subject to variations dependent on the rate of growth &c. of the particular specimen, and in 
many cases the normal surface is hidden by a secondary deposit; and partly because the 
actual density of the corallum is usually increased with age by the secondary deposition 
of lime. 
4. Degree of Coalescence of Branches.—This is a feature which appears to me to be of 
little value unless associated with other characters. Even in species which at a late stage 
of colony-formation exhibit a network of branches, or where the main branches become fused 
into a solid mass, there is no doubt that at an early stage such confluence did not occur. 
For example, there are several specimens of M. efflorescens in the collection of the British 
Museum. The oldest forms a solid vasiform plate in which confluence of the main branches 
takes place quite to the margin of the colony; the youngest has obliquely radiating, non- 
confluent branches with the habit characteristic of M. prolifera, Lamk. Again, the types of 
M. fragilis, B.-Sm., and M. rambleri, B.-Sm., differ only in the latter being an older colony 
than the former ; and owing to the manner in which the branches extend, they are bound to 
become confluent if growth goes on long enough. Evidently, then, the coalescence or non- 
coalescence of branches is an unreliable character, when taken alone, even for specific 
purposes. 
5. Incrusting or Pedicellate Conditions.—Little need be said under this head: apparently 
all species of Madrepora are incrusting in the first instance, and the extent to which incrustation 
takes place is, in some cases at any rate, dependent on environment rather than on the 
habit of the species or group of species. Large incrusting masses occur of species which 
usually form cespitose or even arborescent colonies. The pedicellate condition has also been 
already recognized as not constant in certain species. 
6. Size and Form of the Axial Corallites —These characters were first used by Klunzinger 
and afford valuable assistance in the grouping of species. I am, however, of opinion that 
size alone is of little value. In the primary sections of Klunzinger’s system based on size 
one often has difficulty in fixing the position of a species owing to the fact that the dimensions 
vary beyond those of the section. It would not be difficult in the case of certain species to 
find in one specimen some axial corallites which have the dimensions of one section and 
others of another. LEyidently the divisions 4-6 mm., 3-4 mm., &c. are quite artificial and, 
though convenient for Klunzinger’s purpose, cannot be made use of in a general classi- 
fication. 
With regard to the characters which in the present treatise are regarded as the most 
reliable for the subdivision of the genus, I have already stated that for the present 
any attempt at a classification of the Madrepore must be based primarily on the 
structure of the corallum. ‘This, however, does not preclude an attempt to take into 
consideration the structure and arrangement of the soft tissues in their relation to the 
corallum so far as these are known, and from the basis thus obtained to endeavour to 
distinguish skeletal characters which may be the outcome of a difference in structure or 
arrangement. For instance, in M. cervicornis, Lamk., the corallum is openly reticulate in 
