Mr. J. L. Drummond on a new Oscillatoria. 5 



ving eaten of this matter, had their bones and flesh tinged red 

 as if they had been fed on madder, but without any inconve- 

 nience, as was remarked by Dr. Engelhardt. The same ob- 

 server and M. Frechsel relate that other small fishes which 

 came to the surface for air, or in pursuit of flies, perished after 

 some convulsions when they traversed this matter, either, ac- 

 cording to some, from having eaten of it, or according to others 

 from the mephitic gas at the surface*. 



In the Oscillatoria of Glaslough, the thick conglomerated 

 masses had a heavy but nothing of a mephitic odour like that 

 of O. rubescens, and the plant, so far as I could learn, seemed 

 to have no evil influence on any species of animal, the lough 

 abounding in pike, ells, roach, and perch. I also observed 

 sticklebacks in the shallow parts, and I believe there are also 

 some trout. I found Helix stagnalis and some other lacustrine 

 shells in abundance, and coots and water-hens were numerous. 



From the accounts I received, the green colour is evident in 

 the lough throughout the year, and if I may judge from my 

 own observation, every drop of it is impregnated with the os- 

 cillatory filaments. On examining specimens in the micro- 

 scope, I sometimes observed their motions to be very vivid, 

 and in other instances little or no motion could be perceived. 

 They are extremely minute ; their transverse striae very nume- 

 rous, and at distances of about half a diameter from each other. 



The filaments in the conglomerated masses appeared to me 

 to be many inches long, and running parallel together ; the 

 broken fragments dispersed through the lake cross each other 

 in all directions. Presuming that this is an undescribed spe- 

 cies, I would suggest the specific name cerugescens, from its as- 

 suming the blueish verdigris colour on drying, as being the 

 most characteristic appellation. 



I have only to remark further, that I could perceive nothing 

 peculiar about the lake at Glaslough to which might be at- 

 tached a conjecture as to the growth of one aquatic more than 

 another ; the shore being in some places composed of shelving 

 clay banks, in others flat and muddy, and in others of small cal- 

 careous stones and gravel : one considerable portion is of peat- 

 bog. Among the plants fringing its edge I observed Arundo 



* Lib. cit. part. sec. p. 29 et seq. 



