On Stylaster stelhilatus, &c. By Charles Stewart. 43 
The number of the calicles appears to be increased by fission. 
In the coral the first indication of this is the appearance of the 
points of two styles close together. A bridge stretches between the 
points of the styles. The calicle increasing in size first becomes 
oval, with an increase in the number of septa ; further constriction 
then completes the separation. I have sometimes seen obscure 
indications as if at times the calicles might occasionally arise by 
the simultaneous budding of tentacular and alimentary zooids from 
the surface of the coenosarc. The apparent division of the calicles 
is perhaps really a case of fusion ; this is favoured by the fact that 
the apices of the styles are directed towards one another. But the 
normal number (thirteen) of the septa is the same in a calicle with 
two styles, and increases with their separation, until, when nearly 
complete, they are usually twenty-six. Such an abortion of zooids 
following fusion does not seem probable. 
The chief points in which the corallum of this genus differs from 
that of the Actinozoan corallum, which it in appearance so closely 
resembles, are — 
That it is secreted by the ectoderm. 
That it is permeated by anastomosing canals, which are traversed 
by tubular prolongations of the body wall corresponding either 
with the hydrocaulus or hydrorhiza of other hydrozoa (reminding 
one of the hydrorhiza of Antennularia). 
That the calicles are groups of chambers, the central one for 
the alimentary, the marginal ones for the tentacular zooids. 
That the septa are the remains of the coenenchyma between the 
tentacular zooids. 
And that the theca is but the elevation of the coenenchyma 
around the group of zooids. 
Although many descriptions of the corallum of Tubipora 
musica have been given, I have not seen a notice of a peculiar 
feature which I have found present in nearly all specimens 
examined, but which is particularly marked in one in my own 
possession. This feature consists in the presence of a second tube 
averaging about one-third the diameter of the including theca. It 
is very delicate, and of a pale rose colour ; its thin perforated walls 
appear to be composed of numerous branched flattened spicules 
having a fibrous texture. The tube is generally connected with 
the theca at the points where the plates of connecting coenenchyma 
are found, either by spreading out here into a funnel-like end or 
by tubular branches. 
In the absence of soft parts, one can only speculate on their 
real meaning. It seems possible that by them a communication 
might be kept up between the body cavities of the living zooids on 
the suidace of the corallum and the canals in the tables of coenen- 
chyma, from which budding often takes place. The remains of the 
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