FRESH-WATER ALG. 207 
masses in the ice-cold springs which trickle from 
the edges of glaciers. It may be remarked that 
the alge which conjugate are found only in per- 
fectly still water ; for calmness is absolutely neces- 
sary to enable them to carry out their peculiar 
method of reproduction. They adhere closely to 
paper ; but they lose their beautiful green tints in 
drying, changing to a dull black colour. 
There is a very remarkable class of conferve 
called Oscillatoriz, on account of the singular oscil- 
lating motion observed in the filaments by vari- 
ous naturalists, thus connecting them apparently 
with the animal kingdom ; the power of voluntary 
motion being one of the chief characteristics dis- 
tinguishing animal from vegetable life. These Os- 
cillatoriz grow in masses of filaments based on a 
mucilaginous substance, the remains of old dead 
individuals deprived of their colour and agglutin- 
ated together, the whole emitting a strong odour 
of sulphuretted hydrogen which is extremely dis- 
agreeable, and sometimes causes severe headache. 
As a family they are distinguished for the bril- 
liancy of their colours, their rich gradations of vio- 
let, purple, dark brown, and glossy black, and the 
metallic or eruginous appearance of their shades of 
green. They have been found in a great variety of 
situations, ascending as high as 17,000 feet, or even 
18,000 feet on the Himalayas. Some species grow 
