Monthy My io | Loyal Microscopical Society. 17 
by Mr. Sorby in the May number of this Journal, and by Mr. 
Browning in 1867, I have observed clearly in the living plant, ac- 
companied .by the strong line of chlorophyl in the red, which also 
forms part of the plant’s colour; and of the two lines of Phycocyan, 
that at 44, in the green (characteristic of Mr. Sorby’s red constituent), 
was the stronger. 
Cohn describes his Phycocyan as being the blue colouring matter 
of all the Phycochromacez, which includes many genera besides 
Oscillaria. It is possible that among these genera there may be 
other colouring matters, but it is not impossible that variations are 
caused by the preponderance of either the red or blue element of 
Sorby, and this preponderance may vary with the season or other 
conditions. The spectra from Peltigera, Collema, and Oscillaria, 
given by Askenasy, are all much alike, and differ chiefly in the re- 
lative intensities of the two bands; Mr. Sheppard’s fluid and Cohn’s 
Phycocyan are equally close, but the colouring matters of Peltigera 
and Collema are likely enough distinct from that of Oscillari, 
though this has to be proved. The want of some universal standard 
for indicating spectra is strongly seen in the difficulty there is in 
comparing the statements of these authors. The Phycocyan of 
Cohn, and the colour described by Sheppard, Browning, and Sorby, 
are so similar in properties and mode of occurrence that it appears 
probable that the small differences in their spectra, as figured by 
Cohn and Browning, may be explained away. Whether identical 
or not, they are so closely allied that it will be well to speak of Mr. 
Sheppard’s as the Phycocyan of Sheppard, and Cohn’s as the Phy- 
cocyan of Cohn; it being understood that, as shown by Sorby, a red 
and a blue constituent may be distinguished in these. 
I trust I have not made this communication too long, the pur- 
pose of it being to remove the misapprehension to which your re- 
marks in the annual address relative to Mr. Sorby’s views and my 
own might give rise, and I hope that you will now reconsider my 
ecclesiastical deposition, and if not endow, at any rate re-establish 
the doctrine of 
Yours very truly, 
E. Ray LaAnxester. 
Note.—The President, in forwarding this letter for insertion, desires us to 
state that the establishment of the truth will leave no room for Mr, Lankester’s 
assertion that Mr. Sheppard has “ quite unnecessarily conjured up a mystery.” 
An extract from Mr. Glaisher’s Presidential Address, published in April, 1868, 
gives Dr. Cohn’s view of the mystery in question :—“ Dr. Cohn, in thanking 
Mr. Sheppard ‘ for his highly-interesting communication,’ admits the necess'ty of 
further experiments, ‘that the truth may be established; and after intimating 
his intention to pursue the subject further, he concludes, ‘I shall also endeavour 
to repeat your experiments with albumen, the influence of which upon the colour 
seems very curious after your investigations.’”—Ep. M. M. J. 
VOL. IV. Cc 
