244 THE AMERICAN MONTHLY [Sep 
twig at the bottom was of this brilliant tint. Some float- 
ing patches of Conferve looked like masses of vivid pur- 
ple, without a particle of their normal green being visi- 
ble. The organisms producing this effect were spread in 
a thin layer over everything, and also formed delicate 
filaments lightly attached, which, however, were dissi- 
pated by the slightest movement. On agitating the Con- 
ferve or leaves, the color-containing matter was at once 
diffused through the water. 
Under the microscope it was found to consist of ex- 
ceedingly minute bodies, so small that a very definite 
outline could scarcely be made out with a power of 500 
diameters. These were surrounded by a thin layer of. 
mucilage, and mostly aggregated into hollow spheres; 
many were solitary, but some were gathered in masses. 
The filaments it was almost impossible to examine in 
their original form, but they were composed of the same 
minute bodies disposed more or less in line. A friend 
kindly brought the matter under the notice of a profes- 
sor of botany, who at once identified the organism as a 
bacterium now named Beggiatoa roseo-persicina. He re- 
ferred me te the paper by Dr. Lankester, published in 
“The Quarterly Journal of Microscopical Science’ for 
1873, N. S., vol. xiii. Dr. Lankester there describes, un- 
der the name of Bacterium rubescens, an organism he dis- 
covered in some jars containing putrescent remains of 
animals and plants which had been undisturbed for a 
shert time. The point to which he pays most attention 
is the remarkable color of the “plastids,” which he con- 
sidered. characteristic of the species. There is little doubt 
that it is the same species mentioned by Dr. Cooke in 
his “British Freshwater Algw’’ as Plewrococcus rosco- 
persicinus Rabh., with the remark that it is “certainly 
not a good pleurococcus.”’ He gives the size of the in- 
dividual cells :0015 to ‘004 m. It is not mentioned in 
the same author’s ‘Introduction to Freshwater Alga.” I 
Se 
