86 PROFESSOR RAY LANKESTER. 
as could be prepared by anyone visiting one of the Normandy 
Oyster tanks where the Navicula ostrearia is growing in 
profusion between the beginning of April and the end of June, 
or in September, might be more successful. My observations 
were necessarily confined to small quantities. 
TV. Comparison oF THE CHEMICAL AND SPECTROSCOPIC 
CuaractTERs OF THE Pigment oF NavicuLa OsTREARIA AND OF 
THAT OF THE Marennes Oyster.—The result of a comparison 
of the properties of the blue pigment (to be called Marennin) 
of the Navicula with those of the blue-green pigment in the 
Oyster’s gills, is decidedly favorable to Gaillon’s theory, though 
it must be admitted that the characteristics relied on are rather 
negative than positive. 
In the first place it is important to note that Marennin is 
really blue and not green. When deposited in the Oyster’s 
gill-filaments, which in common Oysters have a yellowish- 
brown colour, it is precisely what we should expect that the 
blue pigment should appear somewhat green, being in fact 
greener in appearance in proportion as the gill is less impreg- 
nated with the abnormal pigment, and becoming of a much 
bluer tint (not greener) when there is much of this pigment 
present. 
Secondly, we note the insolubility of the pigment in both 
cases. 
I have repeated Valenciennes’ observations and can fully 
confirm his statements. The pigment of the green Oysters’ gill 
cannot be dissolved by any treatment: water, alcohol, ether, 
glycerine, benzole, weak alkalis or acids, hot or cold, even 
when their action is prolonged for many hours, fail to dissolve 
it. By strong alkali it may be destroyed, and a brown 
1 Valenciennes notes that weak acids cause the gill to pass from a green 
colour to blue, and that ammonia restores the green tint. This is true, but I 
believe is independent of any action on the special ‘‘ Marennes’” pigment 
itself which is always blue. The change noted is due to an action on the 
yellowish pigment which is normally present in the Oyster’s gill filaments and 
masks the blue pigment. 
