70 HISTORY. 



At the meeting of the British Association for the Advancement of Science, held at Cork, 

 in the same year, I read a paper on Plumatella repens.* In this paper it was attempted to 

 reduce to some sort of order the chaotic accumulation of synonyms by which the species 

 is encumbered. This was facilitated by distinguishing two variations which P. repens'is found 

 to assume, according as it grows upon surfaces of small or large extent, and from not attending 

 to whicli much confusion had arisen ; one of these variations is presented in the " Federbusch- 

 polyp " of Rosel, the other in the " Kammpolyp " of Schaffer, which MUller afterwards assumed 

 as the form on which he founded his species Tuhularia rcpens. The digestive apparatus was 

 also described, as well as the muscles which act on the alimentary canal and invaginated tunic ; 

 it was shown that the latter muscles consisted of two distinct sets, an anterior and a posterior, 

 whose peculiar arrangement was pointed out. 



On the same occasion I [>resented to the meeting a short paper, containing a synopsis of 

 the genera and species of fi-esh-water Polyzoa occurring in Ireland. •!• In this paper 

 two new species of Plumatella and one of Frcdcricclla are described, and the peculiarities of 

 Paliidicella were deemed of sufficient importance to raise this genus to the type of a distinct 

 family among the fresh-water Polyzoa. 



In 1846, I described, in a paper read before the Royal Irish Academy, the locomotive 

 ciliated embryos of Plumatella fruficosa ;^ and at the meeting of the British Association for 

 the same year, presented to that body the result of some observations I had made on the 

 structure of Cristatella.^ The nervous ganglion of this Polyzoon was described, and the mus- 

 cular fibre was shown to be striated, and to have a tendency to break into discs. The 

 statoblasts (or the ova, as I then, in common with other observers, believed them to be), were 

 described as enclosed, during their young state, in a ciliated membranous sac, within which 

 the hooked spines, of which they are at first destitute, are afterwaids developed. 



In the second edition of the ' History of British Zoophytes,' published in 1847, Johnston 

 subjects the portion of his work which treats of fresh-water Polyzoa to a complete revision, 

 and now distributes the British species under the genera Cristatella, Alcyonella, Plumatella, 

 Fredericella, and Paludicella ; he, however, still maintains the specific identity of the " Polype 

 a Panache " with the Alcyonella stagnamm. 



In 1848, we obtain fi-om M. Van Beneden a very valuable memoir on the fresh-water 

 Polyzoa of Belgium. 1| The author here enters into important details of the anatomy and clas- 

 sification of the fresh-water Polyzoa, and gives excellent descriptions and copious synonyms 

 of the several species. After the lapse of nearly a century, he restores to the Alcyonella stay- 

 narum of Lamarck the specific name fungosa originally bestowed on it by Pallas. This is 

 but an act of justice to its discoverer, and ought to be followed by subsequent systematists. 

 Van Beneden also makes the addition of a second species of Alcyonella, which he describes 

 under the name of A.Jlabellum. 



* Allman, On Plumatella repcns. ' Reports of Britisli Association/ 1843. 



f Allman, Synopsis of the genera and species of Zoophytes iuhahiting the fresh Maters of Ireland. 

 ' Reports of British Association,' ISJiS ; and ' Ann. and Mag. of Nat. Hist.,' May, 18-14. 



J Allman, On the Larva state of Plumatella. ' Proc. R. I. Ac.,' 1846. 



§ Allman, On the Structure of Cristatella mucedo. ' Reports of British Association,' 184G. 



II Van Beneden, Recherches sur les Bryozoaires Fluviatiles de Belgique. 'Mem. de I'Acad. 

 Roy. de Belgique,' tome xxi, 18i8. 



