ZOOLOGICAL AND BOTANICAL ASSOCIATION. 165 



On the 27th of August last I made a gathering from a streamlet 

 which passes through the grounds of Delgany Glebe, down a gentle slope, 

 so that the water runs along with considerable rapidity. On a former 

 occasion I had made a gathering from the same place, which produced 

 nothing worthy of notice, for which reason I was not disposed to make 

 a second trial ; but observing the algaj in the channel to be more than 

 usually swollen, I thought the fact indicative of a strange condition, 

 and, therefore, was induced to take a portion for examination. Upon 

 inspection I found Synedra radians occurring frequently, and sometimes 

 in an encysted condition ; the prevailing form, however, was that of 

 Diatoma vulgare, the frustules of which adhering, as usual, by their op- 

 posite angles, formed long filaments of fifty individuals and upwards ; 

 the endochrome was of a green colour ; and the space within the valves 

 was filled with granules (Figs. 1 & 2). 



Upon this occasion I noticed several cysts packed with frustules of 

 Diatoma vulgare, which lay in horizontal layers, packed as cloaely as 

 herrings in a barrel. Nothing of the kind had ever been remarked by 

 me before ; and, lest another opportunity of observing the phenomenon 

 might not be afforded, I took particular notice of every circumstance, 

 and soon discovered that the cysts were not uniform in their appear- 

 ance, but presented different phases, reducible to three distinct and well- 

 marked classes. 



Class A (Fig. 4) consisted of pellucid cysts, in which the included 

 frustules exhibited the same appearance as the free forms, both as re- 

 gards the colour of the endochrome and the disposition of the granules. 



Class B (Fig. 4) included cysts, pellucid like the former, but with- 

 out granules, the frustules, also, having the endochrome more compact 

 than in the free forms, and of a brick-red colour. 



Class C (Fig. 5) contained cysts of a yellowish brown hue, consisting 

 apparently of two envelopes, one within tne other, the interspace being 

 filled with granules ; the frustules included were destitute of granules, 

 and the endochrome compacted into the centre of the cell, and of a brick- 

 red colour. Subsequently, several hundreds of these cysts came under my 

 notice, all reducible to the three classes just described ; the only addi- 

 tional circumstance remarked was, that in variety B the wall of the cyst 

 was more closely pressed upon the mass of frustules within than in 

 either of the other cases. 



Desirous to obtain such information on the subject as was available, 



