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APPENDIX A. (LONSDALE ON CORALS.) 
vertical planes were noticed, as well as re-entering angles formed by the junction of two walls, situated 
obliquely to the general surface of the specimen ; but in every case the flat plane or the re-entering angle 
could be traced upwards or downwards till it passed within the area of a tube, and therefore ascertained 
to be an inner portion of the same tube exposed by fracture ; or if this could not be effected, a careful 
examination of the edges of the planes never failed to prove that they were rough, and that the uneven- 
ness was due to the remains of walls which had projected from them, and had constituted inner sides of 
destroyed columns. In other specimens of the same species, retaining the original substance of the coral 
but having the tubes filled with calcareous spar, not a vestige of the outer surface of a wall could be dis- 
covered; and in others, again, in which the animal structure had been replaced by infiltered matter, 
characters analogous to those of Favosites could in nowise be perceived. 
These differences are believed to be necessary results of the distinct mode by which additional columns 
were developed in each genus. 
In Favosites the additional tubes dependent on the growth of the polypes originated, so far as the author 
is acquainted with the genus, either in gemmules deposited in interspaces or developed on the extreme 
margin of the parent polype. In either instance a perfect individuality immediately took place, and the 
young animal, which rapidly attained considerable lateral dimensions, constructed its tube without the 
area of the parent column, building up the walls unassisted by its neighbours. In almost every example 
the sides of the surrounding tubes are impressed by those of the interposed tube, indicating that the whole 
grew contemporaneously, and that the struggles for space of the vigorous, rapidly expanding young 
polype interfered with the outline of the walls of the full-grown animal, w'hich necessarily possessed, on 
account of its lateral enlargement having ceased, no power to resist such encroachments. From the mode 
of development having been thus wholly interstitial, it is inferred, that the exterior surfaces of adjacent 
walls must naturally and easily separate. It is further inferred, that the polypes at the superior boundary 
of the coral mass had no common connexion, but were perfectly circumscribed and separated. 
The essential manner of developing additional tubes in Chsetetes was, however, by a subdivision within 
the area of the parent. On examining transverse sections (pi. A., fig. 9 a), particularly those in which the 
coral is but slightly coated with infiltered matter, a plate will be frequently seen projecting from one or 
more sides : and by extending the research, similar laminae will be found to range quite across, effecting 
either a simple subdivision into two areas, or a complex one into three or even four. These intersected 
spaces are easily distinguished by the plates springing from sides and not angles. Again, in a vertical sec- 
tion of such specimens, thin, interrupted lamina; will be readily detected, ranging perpendicularly within 
many of the tubes. They are not usually continuous for any distance, but they perfectly agree in their 
nature with the plates just noticed ; and the want of persistence may be rightly assigned to the perishable 
tendency of the coral. Cases, however, were observed of plates which extended without interruption, and 
probably from their first development, for more than an inch. In such examples the walls of the original 
tube ranged regularly upwards, but with a slight divergence, and the introduced lamina, at first not 
quite medial, gradually assumed that position. From this plan of producing additional tubes, it is pre- 
sumed that there could be no natural tendency in the component structure of the walls to divide into 
two plates, as in Favosites ; and, further, that the polypes by which a mass of tubes was formed had a 
community of existence, and were united at the outer boundary of the coral in one animal layer. 
Based on these imperfectly explained structures, the following provisional generic characters are 
proposed : — 
A polymorphous polypidom formed of tubes closely aggregated and traversed by diaphragms ; walls inseparable; 
additional tubes produced by subdivisions within the area of the parent tube, or by extensions of the polype along the 
rnargin of the coral mass. 
