484 REPORT—1885, 
of formative material and certain rudimentary elements, out of which a 
polypide is developed. These two constitute together the primary term 
(Hks.) [germ ?],! of a colony; and by repeated buddings, according to 
the pattern of the species, the composite zoarium is built up. The colony 
is formed by the indefinite repetition of the primitive zooids and their 
modifications.’—Brit. Mar. Poly. p. iv. 
T. Zoacrum. 
In dealing with the zocecium in the various aspects which it presents 
to the student in its dried condition it may be well to mention one or two 
particulars before passing on to special details. In studying the Fossil, 
in connection with the Recent Polyzoa, great caution is necessary in 
making observations on abnormal forms. In the living state we have 
more than one character to guide us in our deliberations ; but in the dried 
state, or in the fossil, very often large portions of the outer crust are so 
calcified that sometimes only the mouth of the cell is visible; possibly 
ocecia or avicularia, hence the necessity of some such plan of classification 
as that afforded by Mr. Hincks, based on persistent characters. Mr. 
Waters, in following Mr. Hincks, when studying the Australian fossil 
Bryozoa, had occasionally the merest fragment of a colony to deal with; 
and had it not been for certain facts on which he could rely with safety, © 
his task must have been almost a hopeless one. These remarks, however, 
apply more particularly to Cheilostomatous groups, such as the MremBRANI- 
poripz and the Escuarm2 of Busk, together with some allied genera 
which will be specially referred to. 
In many cases the primary cells in colonies of the MemMBRANIPORIDE 
are peculiarly shaped. For the most part they are somewhat rounded, 
with a large terminal aperture closed in by a membrane and usually sur- 
rounded by a number of spines. Van Beneden described such a form by 
a distinct generic term, that of Tata, and in connection with the study 
of fossil Colonial growths the Tata stages of the zoarium are very in- 
teresting. Mr. Waters met with some peculiarities in the Australian 
Bryozoa, and I have met with a few examples in the Cretaceous—EKocene 
—Miocene, Crag and Post-pliocene Membranipora of Mr. Hincks. This 
group, however, is broken up by Mr. Busk in his Challenger Report, and 
particulars of the genera, and the characters upon which these are founded, 
are given in the body of the present report. 
In the zocecia of Megapora there is a depressed area surrounded by & 
raised margin, and partially closed in by a calcareous lamina. The aper- 
ture is trifoliate, the upper portion surrounded by spines, similar in some 
respects to Oribrilina radiata and Microporella ciliata. The depressed 
area with the raised margin separates the genus from the other genera in 
this respect, but there are some points of resemblance between Megapora 
ringens, and the Membranipora Flemingii of authors, and the species Mr. 
Hincks thinks ought to be included in the genus Megapora. This latter 
species has also a trifoliate orifice, but the spines of the fully developed 
cell are very different—so also are several other features—of the matured 
and immature cell. 
In the Challenger Report Mr. Busk makes the Membranipora Flemingu 
1 ¢Term’ is used by Hincks, but this may be a misprint for the bracketed word 
[germ ?]. : : 
