ON THE DEVELOPMENT OF LICHENOPORA VERRUOARIA. 135 
the upper ends of the zowcia. The ovicell is increased in size 
by the addition of fresh alveoli. 
What, then, is the morphology of the ovicell? Are we to 
regard it as formed by the fusion of a number of zoccia, repre- 
sented by the constituent alveoli? Or, is the ovicell a highly 
modified zocecium, or two zocecia in cases where two zocecia are 
originally fertile? Or, lastly, is no direct comparison possible 
between Crisia and Lichenopora in respect of their 
ovicells? The last question may probably be dismissed with 
the reply that the fundamental process of embryonic fission, 
and the character of the embryophore, are so similar in the 
two cases that the ovicells must be regarded in general as 
homologous structures. An objection to considering the alveoli 
to be suppressed zocecia is to be found in the fact that the 
zocecia reach the basal lamina of the colony, and the alveoli 
do not. This has previously been correctly pointed out by 
Smitt (20). The alveoli do not, moreover, develop a polypide 
bud at any period. 
We must not lose sight of the fact that Crisia and Licheno- 
pora are two very widely separated genera. It would not, 
indeed, be easy to choose any other pair of recent Cyclostomes 
which would be less nearly related toone another. More light 
will probably be thrown on the morphology of the ovicell of 
Lichenopora by the examination of genera which are less 
different from Crisia. 
I have obviously been fortunate in being able to study the 
ovicells of L. verrucaria. Waters has more than once 
(24, 26) alluded to the importance of examining the ovicells 
of this genus, and has stated that in some species “large 
numbers of specimens may be examined without any ovicell 
being found.” Whether this is due to the absence of the 
ovicells in these cases, or merely to the difficulty of recognising 
them, I have no means of deciding. But it must be expressly 
noted that Waters states (24, p. 261), in describing L. nove- 
zelandiz, Busk, that ‘‘ where there is no ovicell the zocecial 
tubes run into the centre, the central depression forming an 
inverted cone without cancelli;”’ and a similar statement is 
