388 Mr. Hoae’s Observations on the Spongilla fluviatilis, 
be seen dye the paper with permanent colours exactly after the same manner 
as the green chromule of the Spongilla has done. But in order to let the re- 
semblance be more conspicuous, I have also stained the paper (on the left 
side) with the chromule from the leaf of Primula Sinensis, the chromule of a 
common Conferva, and that of Chara vulgaris; and having placed these 
beside the stain derived from the colouring material of the River Sponge, 
every one must be immediately struck with the similitude of their tints. In 
fact, the chromule of the Conferva appears almost identical in colour with 
that of the Spongilla. 
The fourth: if a green piece of this Sponge and any common leaves be 
steeped in strong acid, the effects are likewise to all appearance very similar. 
For instance, I took a living piece of the River Sponge of a bright green co- 
lour, drained off the water, and poured some muriatic acid over it; at first a 
little effervescence took place over the whole surface of the specimen in con- 
sequence of some calcareous matter having been deposited from the water 
upon it; next, the action of the acid began to dispel the green and to turn it 
to a rusty or iron colour*, like as it does when applied to the green of fresh 
leaves. The specimen then became very soft and pulpy, and losing its form, 
put on after a further maceration the same appearance as that which arises 
from a similar effect of muriatic acid upon the parenchymatous substance 
and chromule of any green leaf. 
And the fifth, relates to the disengaging of gas, in all probability oxygen. 
Whilst engaged in my experiments on the action of light upon the colour of 
the Spongilla, I repeatedly observed those living specimens when placed in 
change takes place in the colour of the 
of an alkali, And I will merely mention, that it would be in- 
