ON THE DEVELOPMENT OF LICHENOPORA VERRUCARIA. 795 
Smitt has described correctly the general growth of the 
colony, and he has clearly appreciated the arrangement of the 
alveoli (see below) or interstitial spaces. He has the merit 
of having pointed out that these structures give rise to the 
ovicell, and he calls attention to the important fact that they 
do not reach the basal lamina of the colony. He has further 
stated quite correctly that the central area of the colony, which 
is at the same time an important part of the ovicell, owes its 
character as a space devoid of zoccia to the fact that the area 
originates by the divergence from one another of the most 
centrally placed zocecia. Smitt has also given some account 
of the secondary thickening of the colony. 
The size of the largest colonies (exceeding 8 mm.) recorded 
by Smitt is somewhat greater than that of the largest colonies 
I have found. I have not been able to discover any colony in 
which the ovicell had as many trumpet-shaped openings (one to 
eight) as are described by Smitt. Ido not think that so large a 
number would ever occur in a young colony, in which the 
number seems to be invariably one or two, and in this respect 
I find myself in agreement with Levinsen (12, p. 28) ; but I 
think that it is perfectly possible that a larger number of 
openings are developed in colonies in which a considerable 
number of primary embryos (cf. p. 133) are formed as a second 
generation. I have obtained no actual evidence that this is 
the case, and I have some reason for believing that the larve 
of the second generation make use of the old apertures of the 
ovicells. Ridley has suggested (19, p. 452) that Smitt has 
mistaken zocecia in which incomplete transverse septa have 
been developed for the apertures of ovicells. 
I do not think that Smitt is right when he describes (p. 478) 
the secondary thickening by the formation of the so-called 
“cancelli”’ (cf. my figs. 8 and 9) as giving rise to two or three 
ovicells, arranged in superposed layers. I do not believe that 
there is ever more than a single space which is occupied by 
embryos, although that space can fuse with other spaces by the 
absorption of the calcareous septa which are at first present. 
Smitt describes (p. 476) the first septum formed in the young 
