306 REPORT—1850. 
may admit of some defence, the union of all the other known species with 
this same form must be considered a retrograde step, which, were it not so 
obviously false, might have materially retarded further progress in this de- 
partment of zoology. As it was, however, Raspail’s memoir gave a stimulus 
to inquiry, and a number of investigators now applied themselves to the sub- 
ject with zeal and with a success which might have been expected from the 
advanced state of general zoology, and from the increased means of research 
which improved microscopes had placed in the hands of naturalists. 
Among those who now most materially advanced our knowledge of the 
freshwater Polyzoa, must be especially mentioned MM. Gervais, Dumortier 
and Van Beneden. To Gervais we are indebted for the first complete zoo- 
graphic view of the subject, the determination and diagnosis of the genera 
and their systematic distribution*, while Dumortier and Van Beneden have 
both contributed most important information on the anatomical structure of 
certain species. Wan Beneden moreover has given us a complete memoir 
on the whole of the species inhabiting the freshwaters of Belgium, a memoir, 
which, both in a zoographical and zootomical point of view, is certainly the most 
valuable we possess; while within the present year an excellent paper on the 
anatomy of certain genera, with descriptions of new species, has been published 
by Mr. Hancock ζ in the ‘ Annals of Natural History.’ My own researches 
have been from time to time communicated chiefly to the meetings of this 
Association and of the Royal Irish Academy ; and though they have not been 
hitherto brought together into a connected memoir, they are to be found in 
a detached form in the proceedings of both these bodies. 
All the known forms of freshwater Polyzoa may be included under six 
genera, whose relations and leading diagnostic characters are represented in 
the following Table. These genera embrace seventeen species, sixteen of 
which have already been found in Britain. 
Family. Genus. 
Ceencecium 
free, Wd- SCRISTATELDID AS S.....ccccesvectassevcencce manteucece=<aveteonraete Cristatella. 
2 3 comotive 
a= Ccenceecium sacciform, 
= = ectocyst gelatinous } Lophopus. 
2 5 Ccencecium tubular, 
£5 tubes united, ecto- 
a Ε cyst pergamenta- Alcyonellas 
os Lophophore ceous 
ΞΞ with two } Ceencecium tubular, 
aS long arms tubes distinct, ec- Plumatell 
Coencecium tocyst pergamen- satay 
ἱ rooted } eich eins taceous 
Arms of Lo- 
phophore ΟΝ si ii00, 2255 5ic.Sesoe Ξ παν Fredericella., 
ἰ obsolete 
Lophophore _ orbi- : 
cular, Mouth, ε16- > PALUDICELLIDA 02-000. «οτος saeco -.cte>socces-dscseasabancesaes ao Paludicella. 
stitute of valve 
litane, tom. xii. Van Beneden has been the first to point out the priority of Pallas’s name, 
and in his Recherches sur les Bryozoaires fluviatiles de Belgique, has restored it after a lapse 
of many years; a revision, which justice to the original describer of the species, as well as — 
the laws of Natural History nomenclature, demand, and which I shall gladly follow in the 
present Report. 
* Annales Franeaises et Etrangéres d’Anatomie, 1839. 
+ Van Beneden, Recherches sur les Bryozoaires fluviatiles de Belgique, Mém. de l’Acad. Roy, - 
de Belgique, 1848. 
Ζ On the Anatomy of the Freshwater Bryozoa, Ann. Nat. Hist., 2nd Ser. vol. v. p. 173. 
meas elle «« bee galt Baas ine 
£3 whee 
