304 DESCRIPTION OF CHALK CORALS. 
distributed over the whole surface ; and in the latter the secondary pores are also 
disseminated over the back as well as the front of the branches. 
The point which peculiarly demands attention in an attempt to assign the 
present subject of examination to a generic position, is the nature of the second- 
ary pores, the composition of the coral being extremely simple, and the visceral 
cavities presenting no marked peculiarities. ‘These minor openings belong, as 
already stated, to a tubular structure, which differs from the visceral cavities only 
in dimensions. They varied in number in different specimens, and in different 
portions of a specimen, being prevailingly fewest near the upper extremities of 
the branches and of the lateral pinne ; and most abundant on the sides and in 
the axilla, occupying in those positions the whole surface (figs. 3a, 3b) ; but along 
the front of the ramifications, the number depended on the distance between the 
abdominal cavities, being least where the interspaces were small, and entirely 
wanting when the cavities were separated only by their parietes. In longitudi- 
nal sections nearly coincident with the centre of a branch, small pores were like- 
wise very rare. Viewed generally, a marked distinction was apparent between 
their dimensions and those of the apertures to the visceral receptacles, but some 
among them bore the semblance of partially matured abdominal tubes. It is 
nevertheless believed that no conversion from one condition to the other took 
place; and this opinion appeared to be supported by the observed nature of the 
component parts of the coral. The abdominal cavities to the extent observed in 
prepared sections (figs. 40,4 c) obtained rapidly their full transverse area ; whereas 
the minute tubuli maintained their narrow dimensions. The conical extremities 
of the off-shoots consisted moreover almost entirely of large tubes (fig. 3 a), and 
supported the inference of an early perfecting in that character; while the 
manner in which the size of the branches augmented, strengthened, it was con- 
ceived, the conclusion respecting a functional difference between the two sets of 
tubes. A branch situated near the upper extremity of the specimen represented 
by figure 3, but which had acquired sufficient maturity to have numerous second- 
ary pores, had a breadth of } of a line with a depth of one line ; while another 
main branch near the base of the specimen a line and a quarter in breadth, had 
not markedly increased in depth, indicating a want of relative augmentation, or 
a greater development of visceral cavities on the sides of the branches than in 
the middle ; as well as that a sufficient upward increase had not taken place to 
admit of more than a very limited amount of interpolated abdominal tubes. An 
examination of the same specimen with reference to the distribution of the pores, 
