72 HISTORY. 



always acquainted with the lahours of others in the same field ; and in the case of the 

 fresh-water Polyzoa, it is often extremely difficult to identify his species — a difficulty much 

 enhanced hy the want of exactness in his numerous figures. Under Lamarck's name of 

 Cristatella vagans, he describes the C. mucedo (Cuvier), and is the first after Gervais to figure 

 fully-developed specimens of this beautiful Polyzoon. Under the name of AlcyoneUa gela- 

 tinosa he describes the true Alcyonclla fungosa, while his Alcyonella stagnarum appears to be 

 the young condition of a PlumatcUa. His Plumatella repens would seem to include more 

 than one species, but neither from his descriptions nor figures is it possible to determine the 

 exact animal intended. 



At the meeting of the British Association for 1849, I noticed the addition to the Irish 

 Fauna, of Lophopus crgstallinus, which I had found abundantly in the pond of the Zoological 

 Gardens near Dublin,* and described a new species of Plumatella (P. coralloides of the pre- 

 sent monograph) ; and on the same occasion I described the distribution of the nerves in 

 Phtmatclla repens.^ 



In January, 1850, I presented to the Eoyal Irish Academy, a memoir on the ' Natural 

 History of the genus Alcgonella.''^, This memoir contained a historical introduction to the 

 subject, recorded the addition to the British Fauna of the A. fiahellum of Van Beneden, and 

 gave a detailed account of the anatomy of A. fungosa. The muscles of this Polyzoon were 

 divided into eight distinct sets, the distribution of the nervous system was demonstrated, and 

 the structure of the locomotive embryos was described, and certain errors in the description 

 given by Meyen of these bodies were pointed out. 



In the same year, Mr. Albany Hancoct, already well known by numerous important 

 papers on the anatomy of the IMollusca, but especially by his association with Mr. Alder in 

 their beautiful ' Monograph on the Nudihranchiata,' published an admirable paper on certain 

 species of fresh-water Polyzoa obtained in a small lake in Northumberland. § In this paper 

 the author gives a very full account of the anatomy of Plumatella, Fredericella, and Paludi- 

 cella, characterised by great accuracy, and illustrated by excellent figures, though in some 

 points, as already noted in the anatomical portion of the present work, I have found reason to 

 differ from his conclusions. He also draws attention to the resemblance between the arms of 

 the lophophore in the hippocrepian Polyzoa and the oral arms of the Brachiopoda, and com- 

 pares the arrangement and action of certain muscles in the two groups — important points 

 tending to throw light on the affinities of the Polyzoa. The same paper contains descriptions 

 of new species, which the author records under the names of Plumatella punctata, P. 

 Allmani, and Paludicella procumhens. After carefully considering Mr. Hancock's descrip- 

 tion of his Paludicella procumbeus, I cannot satisfy myself that the characters on which the 

 species is founded are sufficient to entitle it to he considered Ciistinct iwm P. Ehrenhergi ; 



* Allman, On Lophopus crystallhms. ' Reports of British Association,' 1849. 

 t Allman, On the Nervous System and certain other points in the Anatomy of the Bnjozoa. 

 ' Reports of British Association,' 1849. 



+ Allman, The Natural History of the genus Alcyonella. ' Proceedings of Royal Irish Academy/ 



1850. 



§ Hancock, On the Anatomy of the fresli-water Bryozoa, with descriptions of three new species. 



'Ann. and Mag. Nat. Hist./ March, 1850. 



