ON THE DEVELOPMENT OF LICHENOPORA VERRUCARTA. 83 
showing the disc and the proximal part of the funnel, has been 
well figured by Smitt (20, pl. xi, fig. 6). It is obvious that 
the increase of the diameter of the colony is accompanied by 
an increase in the number of zocecia which are present. 
The divergence of the zocecia from the centre of the discoidal 
colony results in the occurrence of a central space, round which 
the zocecia are arranged; and this space is the commencement 
of the ovicell. Two points must be here expressly noticed : 
firstly, that the ovicell is not restricted to certain colonies, but 
is developed in all colonies which reach the proper stage of 
growth; and secondly, that the description of the young ovicell 
must be given with a word of warning. The account of the 
growth of the colony has been taken from entire specimens, 
and largely from dried specimens. In the latter at least, we 
should not expect to find much trace of any structures which 
are not calcareous; and even in dealing with Canada-balsam 
preparations of entire colonies, it is extremely difficult to see 
much of the delicate, uncalcified membranes which really 
exist. But it must here be noticed that the study of sections 
shows emphatically that the various spaces of the colony are 
roofed in by living membranes. Thus the spaces at the growing 
edge shown in fig. 14 are really closed, and the same is true 
of the interzocecial spaces which give rise to the ovicell. Even 
the orifices of the zocecia are not widely-open tubes, but are closed 
during life by a membranous diaphragm, which can be widened 
to allow of the protrusion of the tentacles. Ofall this, nothing 
appears in the dried colony ; but it must be clearly understood 
that the cavity of a young ovicell is morphologically a body- 
cavity, and is not an external space converted into an ovicell 
by the formation of a calcareous roof. 
The development of the ovicell can be most easily described 
after the structure of the complete ovicell is understood. 
Fig. 6 represents a thick free-hand section showing the whole 
length of a single radius of a colony which has not been decal- 
cified. ‘The zoccia diverge from the centre of the colony. 
Each zoecium reaches the attached basal lamina, a short part 
of which it forms. The older zocecia are very much longer 
