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188 SIDNEY F. HARMER. 
course somewhat different from this hypothetical process; but 
I claim to have established the facts (1) that the processes 
which precede the formation of the ovicell take place in a 
fertile zocecium, and (2) that the development of the cal- 
careous roof of the ovicell starts from the region of the orifice 
of the fertile zocecium. 
It remains to be seen whether the ovicells of such genera 
as Hornera, Diastopora, Tubulipora, and Idmonea fit 
in with this idea ; and I hope to have an opportunity of making 
a more extended study of this question. 
Next to the demonstration of the occurrence of embryonic 
fission, a process which had been previously proved for Crisia, 
the most striking fact which I have succeeded in establishing 
is the restriction of the production of an embryo to one or two 
of the oldest zocecia in the normal development. 
Even the second brood of embryos is really dependent on 
this function of the fertile zocecium, or zoccia, of the first 
generation ; for they are nourished in the ovicell which was 
developed in connection with the primary fertile zoccia. In 
the great majority of colonial animals a large number or all 
of the individuals of the colony become fertile. The phe- 
nomena which occur in Lichenopora are perhaps due to the 
fact that the colony in this genus is to be regarded as an 
individual of a higher order. The discoidal form and the close 
association of the zocecia have produced the result that the 
colony behaves in this respect as if it were a single individual. 
The production of fertile eggs is thus limited to one or two 
individuals, and in fact to one or two of the zoccia which are 
first formed as buds from the primary individual of the colony. 
In the case of Crisia, where the association of the different 
zocecia is much less intimate, a considerable number of the 
individuals of a colony may become fertile. Here, however, 
there is something analogous in the behaviour of the inter- 
nodes, each of which in the great majority of species normally 
produces no more than a single ovicell. 
