100 
an explanation of this, as follows : — “ In this modification, the calice of the 
primitive corallite throws up a number of huds ; but the former does not 
seem to feel the stimulus to gemmation till it has reached a great age, and a 
corresponding size. The result of this is, that the secondary corallites remain 
more or less aborted, and do not appear to have sufficient energy to repeat 
the process of budding. Hence, in these cases, we have the fully developed, 
and often comparatively gigantic parent corallite, surmounted hy a tuft of 
small undeveloped secondary corallites, springing from different points on its 
calicine surface.” 1 
In a horizontal section prepared for the microscope, the external wall 
appears as the usual dark circumferential line, sometimes with an inner zone 
of secondary stereojflasma, and sometimes without ; the latter, when present, 
is bounded inwardly by a thin dark ring, which possibly represents the 
primitive theca. If this be so, there is then an intra- and extra-tliecal 
portion; the wall stereojdasma is grey in colour, homogeneous, and dense. 
The supposed primitive theca is, more often than not, absent when the septal 
lamellae abut against the external wall. These lamella) may, or may not, 
consist of primordial septa, represented by dark rods, surrounded by stereo- 
plasma, having a feathery cone-in-cone structure, and projecting a short 
distance into the visceral chambers ; each cone-in-cone mass is separated 
from its neighbour by a thin fluctuating line. In the absence of the 
primordial septa, the surrounding stereoplasma and the fluctuating boundary 
lines are present all the same. The spines also differ in the same section ; 
they may be short, blunt, and triangular, forming a serrated edge to the 
stereoplasmic ring, or a series of definite short spines. 
In a longitudinal section the eye is at first attracted by the thickness 
of the wall stereoplasma, intersected by an occasional primordial septum. It 
will be observed that some of the free ends of the spines are upwardly 
turned, or hooked. The primordial tabula) and their stereoplasmic thickenings 
are also plainly visible. 
PI. XXI, fig. 3, represents a section cut longitudinally and some- 
what obliquely through the septal lamellae immediately before becoming 
spinous ; the primordial septa are distinctly visible. At first sight, these 
would appear to be dissepiments ; but I regard these transverse lines as the 
cut ends of tabulae only. 
1 Nicholson— Trans. R. Soc. Edinb., xxvii, p. 240. 
