ON FRESHWATER POLYZOA. 305 
On the Present State of our Knowledge of the Freshwater Polyzoa. 
By Professor ALLMAN, M.D., F.R.C.S.1., M.RL.A. 
Tue discovery by Trembley* of a compound polypoid animal, which he 
found in the year 1741 in the freshwaters near La Haye, and to which he 
gave the name of “ Polype a Panache,” followed almost immediately by the 
detection of the same animal in England by Bakert, who described it under 
the name of “Bellflower animal,” constitutes an interesting epoch in the 
history of zoology. 
The “ Polype a Panache” was nearly a century afterwards rediscovered by 
M. Dumortier, and described by this naturalist under the name of Lophopus 
_ erystallinus in an-elaborate and important memoir published in the Bul- 
letins de Acad. de Bruxellest. The Lophopus crystallinus presents a fine 
typical example of those polypoid molluscous animals, which, long confounded 
with the genuine polypes, were at last distinguished by the nearly simultaneous 
labours of Grant, Edwards and Thompson, and elevated into a distinct class 
under the names of Polyzoa, Thompson§, and Bryozoa, Ehrenberg |\. 
Thompson’s name has the priority over that of Ehrenberg, and is perhaps 
even more expressive than that proposed by the celebrated zoologist of 
Berlin ; justice to its author therefore requires its adoption, and in the present 
Report I shall employ it instead of the more generally used though more recent 
name of Bryozoa. 
The Polyzoa constitute a class whosé marine representatives are very nu- 
merous, and- which has also examples of great elegance and interest in the 
still and running waters of the land. It is with these freshwater forms that 
the present Report is to be occupied. 
The discovery of the “ Polype ἃ Panache” (ZLophopus erystallinus) is the 
first recorded instance of the detection of a freshwater Polyzcon. This little 
animal had been carefully examined by Trembley and Baker, and both these 
naturalists, in the account they have left us of its structure, have shown them- 
selves acute and faithful observers. It is singular that though Trembley and 
Baker had pointed out all the essential characters of polyzoal structure in 
Lophopus, the significance of their discovery should have remained unre- 
cognized for nearly a century, and that it was not tilla similar type in certain 
‘Maarine polypoid animals arrested the attention of naturalists, that the import- 
ance of this type and its true bearing on systematic zoology began to be 
appreciated. 
The discovery of Zophopus was followed within a few years by that oy 
Plumatella, Cristatella and Aleyonella; but these genera were imperfect] 
distinguished from one another, and our knowledge of their anatomy remaine 
for many years exactly as it had been left by Trembley and Baker. A 
length Raspail{], in 1828, published a very elaborate paper on Aleyonella- 
Elaborate, however, as is this memoir, copiously furnished as it is with well- 
executed figures, it tells us very little of value ; in correctness of anatomical 
detail it falls far behind the accounts left us by Trembley and Baker; and 
though Raspail’s attempt to unite Plumatella repens with Alcyonella fungosa** 
* Trembley, Mém. pour I’Hist. des Polypes d’eau douce, Mém. III. 
‘tT Baker, Employment for the Microscope, part 2. chap. x. 
_ t Dumortier, Recherches sur 1’Anat. et Physiol. des Polypes comp. d’eau douce, Bul. de 
VAcad. Roy. de Bruxelles, 1835. 
: ἃ Zoological Researches, No. 1, 1830. || Symbole Physicez, 1831. 
-{] Raspail, Hist. Nat. de !’Alcyonelle fluyiatile, Mém. de la Soc. d’Hist. Nat. de Paris, 
tom. iv. 
__** The Aleyonella stagnorum of Lamarck was originally described by Pallas under the name 
οὗ Aleyonella fungosa, in a memoir published in the Novi Commentarii Academie Petropo- 
1850. x 
/ 
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