52 W. G. RIDEWOOD. 
In specimen D, as in specimen ©, the manner in which the coenoecium of the 
polyzoon—in this case Menipea—has become embedded in the test of the 
Cephalodiscus gives one a good idea of the profusion with which this material is 
secreted, 
The shape of the tubarium of specimen G differs materially from that of the type 
specimen, but that G belongs to the same species as A is evident from the size of 
the spines, the size and relations of the few tubular prolongations of the test that 
can be recognised, the size of the ostia, and the characters of the polypides. 
Specimen G is evidently a young colony of Cephalodiscus hodgsoni which has not 
yet assumed the racemose appearance presented by the type specimen. ‘The 
polypides are crowded underneath a square inch or so of the calcified reticular 
coenoecium of the polyzoon Fetepora, in relation with which the colony has 
established itself. They are supported upon a fairly flat floor of test secreted by 
themselves, and the upper surface of the Metepora is also coated with a thin, flat 
sheet of the same material. From around three-fourths of the edge there stand 
out fifty or sixty spines, mostly simple and unforked, and radiating more or less 
obliquely outwards from the centre of the whole structure. Some of these spines 
are arranged in groups of four or five around the openings of ten or eleven 
short tubes which lead out from the marginal parts of the flattened central 
chamber. 
This specimen (G) is interesting because Harmer, in describing the species 
C. sibogae, attaches some importance to the crowding of the polypides in a low and 
wide “basal encrustation” with irregularly divided cavity, set upon the piece of 
rock on which the colony was growing (10, p. 13). That Cephalodiscus sibogae is 
a valid species I do not doubt, but this particular “habit” of the colony will 
probably prove to be common, in the earlier stages of growth of the colony, to 
most, if not to all species of Cephalodiscus, except those which, like C. levinseni 
and C. nigrescens, have separate tubes for each polypide and its buds. 
Polypides. 
It is remarkable how densely crowded are the polypides in this species; yet, 
although they are in such close contact, the only organic continuity which exists 
is that between the parents and their buds. If one side of the tubarium be removed 
and the contents carefully isolated, the crowd of polypides can be unravelled into 
a number of separate individuals, with their buds. The apparent connection is 
due to the entanglement of the stalks of the buds of the different individuals. 
Judging from the least crowded parts of the colony it is evident that, as in 
C’. dodecalophus, each polypide is free to pass out through the ostia of the tubarium, 
and to move about from end to end of the interior, except in so far as it may 
be incommoded by the crowding of the other polypides. 
