ALLMAN ON THE ERESH-WATER FOLYZOA. 
61 
the first of which gives us an account of the anatomy and physiology 
of the Polyzoa as a class; while the second embraces the history and 
bibliography of the subject, and describes the specific characters of the 
fresh-water forms. The geographical distribution and habits of the 
Polyzoa are also considered. 
In the brief space at our disposal, any attempt to convey an outline 
of Dr. Allman’s views on the anatomy of the Polyzoa would be evi¬ 
dently impossible. We might, however, be permitted to remark that 
the thanks of naturalists, to which he is entitled for the introduction 
of a precise nomenclature into our descriptions of the Hydraform Zoo¬ 
phytes (vide Dr. Allman on “ Cordylophora lacustris,” Philosophical 
Transactions, 1853), are no less due to him for performing the same 
task in the case of the Polyzoa. The nomenclature referred to, and 
the reasons which induced him to adopt it, are best explained in his 
own words:— 
“ The old notion, which, by mistaking the zoological rank of the Polyzoa, erroneously 
referred them to the class of the Polypes, caused the same terms to be applied to them 
which were also used to designate the various parts of the true Polypes. The recogni¬ 
tion, however, of a type of structure in the Polyzoa totally distinct from that of the 
Polypes proper, necessitates a change in the terminology employed in their description. 
On these grounds I have ventured to substitute some new terms for those previously 
used, while our increased knowledge of Polyzoal structure necessitates the use of certain 
additional terms, of which we have no representations in the descriptive terminology of 
previous authors. For the term Polypes, therefore, originally applied not only to the 
Polypoid Kadiata, to which its use ought to be confined, but also to the retractile portion 
of the Polyzoa, I have substituted in the following memoir that of Polypide. To the 
common dermal system as a colony, which, as well as the solid basis of the true Polypes, 
was formerly known under the names of Polypary and Polypidome, I have applied the 
terme Ccencecium. The coenoecium is composed almost universally of two perfectly dis¬ 
tinct tunics; to the external I have given the name of Ectocyst , and to the internal 
that of Endocyst. The sort of disk or stage which surrounds the mouth, and bears the 
tentacula, I have called Lophopliore. The Epistome is a peculiar valve-like organ, which 
arches over the mouth in most of the'fresh-water genera. The Perigastric space is the 
space included between the walls of the endocyst and the alimentary canal.” 
The several parts here indicated, the modifications which they un¬ 
dergo, and the functions they perform, are then minutely described, as 
is also the complicated muscular system which the Polyzoa possess. 
The nervous system in these animals consists of a single ganglion, from 
which several filaments are given off. In all the species which Dr. 
Allman has examined, with one exception (Paludicella), such a system 
has been found to exist. 
The Molluscan type of structure manifested by the Polyzoa, and the 
remarkable homologies which they present to the Tunicata, are ex¬ 
plained at some length, and the author compares his own views with 
those of Mr. Huxley on the same subject. The results of the recent in¬ 
vestigations of Krohn and Leukart into the development of the Polyzoa 
are considered in reference to this important relation. The connexion 
of the Brachiopoda with the other Molluscoida, as maintained by Mr. 
Huxley, is viewed in a different light by Dr. Allman. We would will¬ 
ingly stay to discuss these interesting questions, did our limits permit of 
so doing. 
