BREAKING OF THE MERES. 113 
with these two species of Chcetophora in Rivularia , is evidence of 
its relationship having been appreciated. 
Another quotation which we purpose adding is from “ The 
Annals of Natural History” (April, 1840), by W. Thompson, on 
“ An Alga which Colours Ballydrain Lake.” He says, “ On 
visiting the lake (July 15) to-day I found that the whole body of 
water was tinged with a dull faintly glaucous hue. On going out 
in a boat to ascertain the cause of this appearance, I saw that the 
water was everywhere filled with extremely minute particles, which 
might be compared to the motes in a sunbeam. To the unassisted 
eye they seemed as delicate as the finest human hair, and of a 
spiral form. On enquiry I learned that the appearance had been 
observed only for the last four or five years, and for about three 
months in each year. One of my friends had looked upon its 
approach with dread, as it interfered so much with his angling, 
that during the period of its continuance this sport had to be 
abandoned.” Subsequently the plant was observed as late as the 
27th September, but on October 7th all had disappeared. In the 
following year the Alga was seen first on the 3rd of July, and 
last on the 23rd of September. 
“ The specimens obtained were invariably of similar breadth, 
and rarely presented more than four spiral turns, and when of this 
size were l-50th of an inch in length. The species at first, when 
mingling with the water, is of a dark green colour, when in calm 
weather it ascends to the surface in separate particles it appears 
pale green ; when it does so en masse (the earliest symptom of 
decay) it is of a pale blue, and in the last stage of decomposition 
ferruginous. When two of the spiral portions come in contact 
they have an elastic power, by which they can, though slowly, dis- 
entangle themselves, and separate from each other.” The alga, 
of which the above is only an abridged account, was called Ana- 
bcena spiralis by Mr. Thompson, but has been transferred by Ra- 
benhorstto Spirulina, to which genus it undoubtedly belongs, as 
Spirulina Thompsoni.” 
In the same communication is a brief account of the occurrence 
of Anabaena flos-aquaz, Bory, tinging in a similar manner “ with 
its delicate green hue the margin of the smallest of the lochs 
Maben, in Dumfriesshire, on the 15th of August, 1838.” 
Also of Aphanizomenon recurvum , Morren (now referred to 
Sphcerozyga Jios-aquce), found floating on the surface of sheltered 
creeks in Ballydrain Lake, having the appearance of powdered ver- 
digris. Mr. Thomson says of it : — “ In Ballydrain Lake I have, 
both in 1838 and 1839, remarked its presence in very calm days, 
for it is only at such times visible, during the months of July, 
August, and September, and then it appears in the most sheltered 
creeks only, floating in patches of various dimensions.” 
The last of the series of quotations will be from the first number 
of the “ Annals of Natural History ” (vol. i., p. 1) : — “ On a New 
Oscillatoria , the Colouring Substance of Glaslough Lake, Ireland,” 
by Dr. Drummond. He commences by stating that t% Glas-lougli ” 
signifies “green lake,” an appellation given to it from time im- 
