240 On a Pterobranchiate Poly zoon from Canada. 



Fig. 1. 



Fi°\ 2*. 



" The common substance of the colony, resembling sarcode, 

 is in masses of some extent, 1| inch deep, and has the little 

 animals protruded all over it. The ciliated tentacles, about 

 100 in number, in four rows on two finger-like extensions, 

 the distinct anal canal, and the nervous ganglion leave no 

 doubt of the creature being a Polyzoon of the order Hippo- 

 crepia. The ova (statoblasts) are also abundant, with their 

 marginal anchor-like hooklets ; but it does not 

 seem to me to agree with any of the genera 

 which I can find described ; much less can I 



determine the species The two branches 



of the lophophore do not form a horseshoe figure, 

 but are more entirely separated, thus (fig. 1). 



I add a faithful though rude sketch of 



the Polyzoon (fig. 2) , seen in one direction ; it 



does not show the flexure of the alimentary canal, but it 



shows the lophophore well ; and if you plant the animal as 



one of a multitude on a gelatinous or 



sarcode mass (polyzoarium) common to 



them all, you will have a right idea of 



its life." 



The remarkable feature of this Cana- 

 dian Polyzoon is the tentacular corona, 

 the peculiarity of which is insisted on 

 in the description, and clearly shown in 

 the accompanying sketch. The tenta- 

 cles, instead of being disposed in a horse- 

 shoe figure and forming a continuous 

 series, as in the ordinary freshwater (or 

 Phylactolsematous) species, are borne on 

 two distinct erect lobes, which are sepa- 

 rated at the base. They constitute, 

 therefore, two series, which are ranged 

 along the edge of the finger-like processes. 

 The structure of the corona, in fact, ex- 

 actly resembles that which we find in the 

 genus Rhabdopleura, Allman, and which 

 is characteristic of the Pterobranchiate 

 group of Polyzoa. In what other points the Canadian species 

 may differ from the typical form of the Phylactolgemata, or how 

 far it may agree with it in general character, we have not at pre- 

 sent the means of judging ; but we have, I think, sufficient 

 ground for believing that there exists in the fresh waters of 

 Canada a Pterobranchiate polyzoon which is separated from 



* This figure, though not a facsimile of the original drawing, accu- 

 rately represents its essential points. 



