40 VINE : CLASSIFICATION OF THE PALAEOZOIC POLYZOA. 
complete history of all that has been attempted in the way of 
arrangement, we must mention the efforts of Dr. H. Hamm."'-' Dr. 
Hamm, however, in his new classification and on very slender basis 
creates fourteen new genera of fossil Cyclostomata. " It is not new 
genera or families that are wanted ; the real difficulty is to deal 
with and show the connection of those now used." Further on 
(p. 680) Mr. Waters says " Mr. Vine has brought together in the 
British Association Reports a vast amount of material bearing upon 
the classification of the Cyclostomata up to the age of the Cretaceous. 
. . . For my own part I much doubt if we are yet in a 
position to frame anything approaching to a natural and final classifi- 
cation of the older forms, but this opinion may arise from my 
extremely small acquaintance with Palaeozoic Bryozoa ; but neither 
do I think we have nearly arrived at that point with the recent and 
neozoic forms, and until this is the case we can hardly expect to be 
quite sure about the older ones ; and I have often urged upon my 
friend Mr. Vine that more information concerning the minute struc- 
tures would be most valuable from so good a worker." In answer to 
the question what are Polyzoa — 
Mr. Hincks saysf " The Polyzoa are almost universally composite 
animals, forming colonies of considerable extent, which are the 
products of repeated continuous gemmation." In every Polyzoon 
we distinguish two fundamental elements, the Zocecium and the 
PoLYPiDE. These are the primary Zooids in every colony." Professor 
H. A. Nicholson says I" All the Polyzoa live in an associated form 
in colonies . . each ' Polyzoarium ' (or colony) consists of an 
assemblage of distinct but similar Zooids arising by continuous gem- 
mation from a single primordial individual. The colonies . . . 
are in many respects closely similar to those of many of the Hydroid 
Polypes .... The ' Polyzoarium ' or ' Coenecium ' however of 
a Polyzoon differs from the Polypidom of a composite Hydroid in the 
general fact that the separate cells of the former do not communicate 
with one another, otherwise than by the continuity of the external 
* Die Bry. des Mastr. Ober-Senon, 1 Th. Cycles, Berlin, 1881. 
f Introduction Brit. Marine Polyzoa. pp. i and iii. 
X Manual of Palaeontology. Vol. I, p. 414, Ed. 1879. 
