ZOOLOGICAL AND BOTANICAL ASSOCIATION. 121 



this state a withdrawal of the endochrome, leaving a little clear space at 

 the ends, of a somewhat triangular outline, as if hounded on two sides by 

 the outer wall, and in which there is sometimes to be seen a detached 

 granule ; but I am not able to make out that this moves. But even in 

 this altered state of S. obscura (as in Scenedesmus), its oblique mode of 

 division, and consequent unsymmetrical outline, will easily distinguish 

 it from the form under consideration. 



Indeed, this form to me appears very distinct from any other de- 

 scribed, and though I have contrasted it with others (almost unnecessarily 

 in some cases), a moment's inspection of recent specimens would, I think, 

 on this point convince any observer. I shall, then, describe this species 

 as follows : — 



Penium Berginii (». «.) 



Frond minute, about three or four times longer than broad, smooth, 

 fusiform; segments cuneate; ends roundly pointed; endochrome irregular, 

 or sometimes with more or less evident longitudinal fillets, also with a 

 transverse pale band, and having close to each end of the frond a con- 

 spicuous, well-defined circular cavity, containing moving granules, and 

 each half usually having immersed in the rest of the endochrome a single 

 central spherical corpuscle. 



Length of frond, xhs to rhy of an inch ; greatest breadth, vhrs of an 

 inch ; diameter at the ends, t&v of an inch. 



I feel very happy in being accorded the privilege of naming this spe- 

 cies after the well-known microscopist, Thomas F. Bergin, Esq., M.R.I.A., 

 President of the late Microscopical Society of Dublin ; while I trust that 

 gentleman may look upon this trifling compliment as a mark of unaf- 

 fected, but sincere, respect for his numerous scientific attainments, and 

 more especially in regard to microscopy, the active pursuit of which has 

 been interrupted owing to delicate health, at once greatly to be la- 

 mented for his own sake, as well as much to be regretted for the cause 

 ofscience. 



I have thus endeavoured to give my own ideas as to the various new 

 forms, or other matters to which I have directed attention. In regard 

 to my new filamentous form there can be no doubt that it is a Desmid, 

 and as I could not satisfactorily to myself refer it to any genus described, 

 I had hence no alternative but to attempt to make a new genus to 



ZOOL. & BOT. PBOC. SOC — VOL. I. B 



