36 



Believing that the utiHty of field operations is not full}' 

 appreciated, I am induced to place before you a sketch 

 of three minor natural history expeditions, made during 

 the last meeting of the British Association in Dublin. 

 The first was under the direction of Dr. AUman, Professor 

 of Natural History in the University of Edinburgh, a 

 worthy successor to Professor Edward Forbes, both in 

 talent and that honhommie which made the late Professor 

 as much beloved, as his extraordinary genius caused him 

 to be respected. We met in Sackville Street, at eleven 

 a.m., our object being to occupy the time until two p.m., 

 by exploring the localities in which Dr. Allman had 

 discovered and studied the species of fresh-water polyzoa, 

 which he has so fully described in his masterly mono- 

 graph. Our party consisted of Dr. Allman and his 

 brother. Professor Redfern, the Rev. H. H. Higgins, 

 the Rev. H. Wood, F.G.S., Dr. J. B. Edwards, and 

 myself. We first directed our steps to the Dublin 

 canal. Here most of us were astonished at the green 

 colour of the water, diifering altogether from the green- 

 ness which results from stagnation. It appeared to be 

 almost filled with green fusiform spiculfe, each freely 

 floating. Upon examination, these proved to be the 

 curious little fresh-water confervae, Aphanizomenon in- 

 curvum and A. flos-aquae, the Spherozyga spiralis of some 

 authors, and Trichormus spiralis of Allman. For at least 

 half a mile, which we went along the banks of the canal 

 and aroimd the docks and basins, we saw this little plant 

 in countless millions, generally fi'ee as before mentioned, 

 but occasionally aggTegated into masses, apparently 

 where it had clung to the walls or projecting weeds. 

 These clusters had a bright apple-green colour, and 

 appeared smooth and compact, reminding us of the 

 curious NostocJiincv, but upon the slightest touch the frus- 

 tules were disunited, and floated away independently, 



