284. MEMORANDA. 
sense, dichroic; and neither of these are “‘ the result of de- 
caying,” but are contained by living alge. Mr. Sorby agrees 
with me (in a letter received a few days since) that Mr. 
Sheppard’s colouring matter is identical with that which 
Cohn calls “ phycocyan,” and which is found in plants 
allied to Batrachospermum. It is hardly necessary for me 
here to quote the account of this substance given in your 
last Quarterly Chronicle. It agrees with Mr. Sheppard’s 
substance, in forming a pale blue solution in water (with a 
strong carmine fluorescence), from which it frequently pre- 
cipitates as a jelly. Dr. Cohn gives a drawing of the spec- 
trum of Phycocyan, which I have compared with Mr. Brown- 
ing’s drawing, and I have found them to agree, though 
Cohn has used a prism of greater dispersive power than that 
made by Mr. Browning. ‘There can be no doubt in the 
mind of an unprejudiced observer that this is the history of 
Mr. Sheppard’s coloured solution, which does away with its 
mystery without lessening its real interest. I may just say 
that the red colour of Protococcus, &c., is a very different 
body, being a scarlet monochromatic oil known as hemato- 
chrome.—E. Ray LanKestER, Christ Church, Oxford. 
Corethra plumicornis—IJn the bricf summary (‘ Trans- 
actions,’ p. 99) of the principal points of interest appertain- 
ing to the structure of this transparent creature, the author 
has not deemed it advisable to complicate the narrative, by 
references to the labours of other observers. Any one, how- 
ever, who may wish to prosecute the study of its anatomy 
will find that the microscope has not been idle in recording 
the wonders of its organization. In the ‘ Popular Science 
Review’ for October, 1865, Mr. Edwin Ray Lankester 
published an excellent paper on the subject, while on the 
Continent Leydig, of Tubingen, has written largely on the 
nervous system and on the structure of the heart (** Anatom- 
isches und Histologisches tiber die Larve yon Corethra 
plumicornis,” in Siebold and Kélliker’s ‘ Zeitschrift, B. 3, 
8. 435). A monograph by Karsch, ‘De Corethra plumi- 
cornis metamorphosi,’ may likewise be advantageously con- 
sulted. But the most elaborate account of its anatomy and 
general history is given in an admirable paper by Dr. August 
Weismann, “ Die Metamorphose der Corethra plumicornis,” 
in Siebold and KGlliker’s ‘ Zeitschrift’? for October, 1866 
Bd. 16, 8. 45. : 
