DESCRIPTION OF CHALK CORALS. 287 
surfaces however the same elements, with the exception of tubular mouths, are 
detectable as in young and perfected states, or rows of pores with intermediate 
laminze, the essential difference being a great augmentation in the number of the 
rows, and a diminution in the boldness of the lamine. This is another instance 
of the necessity for not regarding the viscera and associated tentacula as the 
only constituents of the polype. 
Longitudinal sections (fig. 7d) gave more or less decomposed centres, but the 
best-preserved portions consisted of an axis of very slightly diverging, elongated 
tubes with slender interspaces or united walls ; and on each side an outer band in 
which part of an almost horizontal extension of a tube was occasionally visible. 
Where the abrasion had not penetrated to the centre, the space between the ob- 
liquely intersected tubes exhibited minute pores and fine longitudinal lines ; and 
the side bands showed throughout similarly arranged pores and lamine ; the 
whole of the interior presenting clear proofs of an inward continuation of outer 
structures. A transverse section (fig. 7 e) afforded equivalent characters, or a 
middle area composed of closely aggregated tubes increasing in size at the cir- 
cumference, and a surrounding zone of considerable breadth, in which faint con- 
verging white lines could be perceived, also indications of pores, and very 
markedly two horizontally extended tubes. 
Among the deviations from a regular construction, the following were noticed : 
first (fig. 7 f), irregular spaces without apertures to visceral cavities, and occupied 
wholly by pores and longitudinal lamine (consult Roemer, fig. 29 d): secondly 
(fig. 7g), fragments which exhibited in the lowest portion regular mature charac- 
ters, but midway a surface entirely porous, like that of aged conditions, a per- 
fect gradation being evident from the regular to the abnormal state: thirdly 
(fig. 7 h), slender branches with totally irregular developments ; the mouths being 
unequally distributed, very prominent, and occasionally covered by a solid plate, 
the subordinate structures being also very defective or indistinct. Deviations in 
the range of both primary and secondary ribs were common, as well as inter- 
minglings of the above and other variations. 
The visceral tubes sprung solely from the centre of the coral, and formed 
simple hollows in the general fabric, being destitute of a distinct wall or lining ; 
and their thoroughly foraminated sides afforded abundant canals for the trans- 
mission of nourishment and calcareous matter from the digestive organs to those 
portions of the polype which occupied or constructed the framework. 
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