Monty eh | Royal Microscopical Society. 15 
England for drawing so many persons’ attention to the subject. 
In my letter, which you have considered to be disestablished by Mr. 
Sorby’s paper, I express the opinion that Mr. Sheppard’s coloured 
fluid probably owes its colour to Cohn’s Phycocyan, or a closely- 
allied body, and that opinion is shared by Mr. Sorby and everyone 
else with whom I have conversed who has looked into the question, 
and I am unable to see in what respect Mr. Sorby’s observations 
confute my views, since they are almost identical with’ his own. 
Mr. Sheppard declared that his coloured fluid could not have re- 
sulted from the algze which were present, most emphatically. Now 
I imagine there is no one who will not admit that it does result 
from decaying alge (the colour existing in living alge at first), 
which I stated in the letter supposed to be disestablished, and which 
Mr. Sorby fully endorses in his paper, speaking, as he does, of the 
confervoid growth “decomposed with water” and “decomposed 
with albumen.” 
The fact is, Sir, that, word for word, I am prepared to repeat 
the letter published in 1867, and beg your readers to turn to it in 
order to spare your space. They will find that, so far from being 
disestablished, the view which I expressed—which was the simple, 
straightforward one—is the view which everybody takes—probably 
Mr. Sheppard himself—at the present time. 
There are two important facts indicated in Mr. Sorby’s paper 
which have nothing whatever to do with the above matter, but 
which I will here mention. He endeavours to show that from Mr. 
Sheppard’s two-banded fluorescent fluid—which I am inclined to 
consider identical with Cohn’s Phycocyan, but which Mr. Sorby, 
not having seen Cohn’s paper, does not feel sure about—a single- 
banded blue and a single-banded red fluid may be obtained. He 
succeeds in obtaining the red fluid from the two-banded fluid of Mr. 
Sheppard by the action of absolute alcohol. The single-banded 
blue fluid he has obtained from fresh specimens of confervoid growth 
“decomposed with water.” The separation of these two colours is 
important, but it does not in the least affect their relation to the 
Phycocyan of Cohn, for the spectrum of Phycocyan as figured by 
Cohn is two-banded (except a very faint line at 9), and agrees with 
that of Mr. Sheppard’s fluid, if we make allowance for strength of 
solution and difference. of spectroscopes. The second point which 
Mr. Sorby makes out is an action of albumen in promoting the for- 
mation of the second constituent of Mr. Sheppard’s solution. This 
is very different from the action which Mr. Sheppard supposed he 
had made out, namely, that the albumen was converted into a colour- 
ing matter by monads. Mr. Sorby seems to think that the albumen 
really takes part in promoting a chemical change of the cell con- 
tents or of the colouring matter of the Oscillarie. If it does, its 
action is merely “catalytic,” as chemists say; but I believe that it 
