PLUMATELLA REPENS. 93 



would feel at first inclined to attribute to it. Indeed, the tendency to the formation of trans- 

 verse septa would seem to occur generally throughout Alajonella, Plumatella, and Fredericella, 

 while in Paludicella these septa acquire their maximum in development and constancy, and 

 become thus one of the most striking features of the Polyzoon. 



In drawing out the diagnoses of the species of Plumatella, I have availed myself of the 

 same class of characters as those which were used for a similar purpose in Alcyonella, namely, 

 the general habit of the animal, the presence or absence of the furrow in the ectocyst, and the 

 shape of the statoblasts. The number of the tentacula also, and the more or less plicated or 

 festooned condition of the edge of the calyciform membrane are generally introduced into the 

 specific character. It must be recollected, however, that unless the difference in the number 

 of tentacula amounts to ten or fifteen, it can scarcely be relied on as a specific character, and 

 the condition of the calyx, though perhaps really of sutficient constancy to form a good cha- 

 racter, is often very difficult to determine. These last two characters can in general, therefore, 

 only be considered as of secondary value, and merely adjuvant to the former. 



Generic character. — Coencecium confervoid, branched, composed of a series of membrano- 

 comeous tubular cells, each of which constitutes a short ramulus with a terminal orifice; 

 branches distinct from one another. Lophophore crescentic. Statoblasts elliptical, with an 

 annulus, but without marginal spines. 



Number of known species twelve, of which nine are British. 



1. Plumatella repens, Linnaeus. PI. V. 



Specific character. — CcEnoecium irregularly branched, cells sub-claviform, destitute of 

 furrow and keel. Tentacula about sixty ; margin of calyx distinctly festooned. Statoblasts 

 broad. 



Variation a. — Coencecium closely adherent, creeping along the surface of various sub- 

 merged bodies, to which the branches are attached in their entire length. (PI. V, figs. 1, 2.) 



Variation /3. — Ccenoecium attached only towards the origin, branches soon becoming 

 fi-ee. (PI. V, figs. 3, 4.) 



Synonyms. 



It is scarcely possible to conceive of a species burdened with a more discordant and 

 perplexing synonymy than that which encumbers the history of P. repens. In order to reduce 

 this chaos to some sort of order, the first step is, of course, the determination of the exact 

 animal which the original founder of the name had in view in his description. 



In the tenth edition of the ' Systema Naturte," published in 1758, we find Linnaeus intro- 

 ducing an animal under the name of Tubipora repeats, and placing it amongst his Lithophi/ta 

 with the following diagnosis : 



" T. corallio repente filiformi dichotomo : tubis flexilibus cylindricis distantibus erectis. 



" Habitat in aquK dulcis plantis in Nymphaea, &c., minuta." 



The figures here referred to are Trembley's " Polype a Panache," as copied by Ba;ck in 

 ' Acta Suecica,' Rosel's figures of his " Federbusch-Polyp," and Schaffer's figures of his 



