ON THE DEVELOPMENT OF LICHENOPORA VERRUCARIA. 81 
cut on p. 78 (IV and V) shows that 2? and 2 are at their 
bases symmetrical with regard to z!, and are clearly a pair of 
sister zocecia produced by the primary zocecium of the colony. 
Figs. 2 and 14 illustrate further the manner in which the 
number of zocecia becomes increased. This happens by the 
forking of a pre-existing septum ; and the zoccia are at first 
bounded externally by the common growing rim of the colony. 
The way in which the zocecium is completed externally is shown 
in fig. 14, which represents a part of the growing margin of an 
old Lichenopora. No sooner is the outer wall completed 
than the zocecium commences to grow upwards as a free tube, 
although its inner side has before then commenced its upward 
growth. ‘The obliquely truncated character of the adult orifice 
is thus a marked feature even at the first formation of a 
zocecium. 
Fig. 14 shows that the septa do not reach the actual rim of 
the colony, and that the outer wall of the zocecium always 
grows up from within the edge. Since this happens in the 
entire circuit of the mouth of the funnel-shaped colony, part 
of the rim capable of forming new zoccia is left all round, and 
this is the proximate cause of the assumption of the completely 
discoidal shape which is so characteristic of the genus Lichen- 
opora. The growing edge is well seen in figs. 38 and 4, from 
which it is evident that that part of the rim which is situated 
on the proximal side of the first three zoccia grows at first 
much less energetically than the opposite part. 
We may here notice an important generic difference between 
Lichenopora and such a genus as Tubulipora. In the 
latter, z! and z? are formed in such a way that the proximal 
part of the rim of the young funnel-shaped colony is used up 
in forming their outer walls. There is thus no edge capable 
of giving rise to new zocecia between z! and z? on the one 
hand and the disc of fixation on the other hand. The colony 
thus assumes a fan-like shape instead of the discoidal form 
which is assumed by Lichenopora. This distinction has 
already been pointed out by Smitt (20, p. 476). 
Fig. 4 represents a right-handed colony of Lichenopora 
vou. 39, PART 1.—NEW SER. F 
