88 PROFESSOR RAY LANKESTER. 
important link in the chain of reasoning by which the colora- 
tion of the Oyster’s gills is connected with the blue pigment 
(Marennin) of Navicula ostrearia, is found in an examina- 
tion of the contents of the alimentary canal of a “ huitre de 
Marennes ” when in full colour. 
The examination of these contents with the microscope 
suffices to demonstrate that the Navicula is taken in enormous 
quantities by the Oyster. Not only do we remark the dark 
blue-green colour of the contents of the alimentary canal, but 
we find the siliceous shells of the Navicula ostrearia in 
enormous numbers. 
Gaillon was at some pains to prove that Oysters do not eat 
floating green alge of large size, and that in consequence the 
green colour of the gills of the “ huitres de Marennes” was 
not due to the chicrophyll of such organisms. 
It does not appear to have occurred to him to make a micro- 
scopic study of the contents of the Oyster’s alimentary canal, 
which would have furnished him with a simple demonstration 
of the fact that the Oyster does not take in such coarse 
material into its alimentary canal, and does take in the 
Navicula ostrearia, as he inferred but did not prove by 
direct observation. 
VI. Microscopic APPEARANCES OF THE GREEN OysTER’s 
Gitt and Mope or Distrisution oF tHE PicMENT.— 
Modern methods of microscopical investigation enable us to 
obtain a much more detailed knowledge of the Oyster’s gill and 
of the exact position of the pigment which gives the green 
appearance to the “ Marennes” oyster than was possible in the 
time of Gaillon (1820), or even of Valenciennes (1840). Valen- 
ciennes expressly states that the pigment in the Oyster’s gills 
“offre rien de remarquable 4 |’examen microscopique.” 
After describing the peculiar chemical properties of the pig- 
ment he arrives at the conclusion that it is ‘an animal matter 
distinct from all green organic substances hitherto studied,’ 
and further suggests that it is a peculiar modification of the 
bile which is assimilated, and fixes itself in the parenchyma of 
