ON GREEN OYSTERS. vp: 
On Green Oysters. 
By 
E. Ray Lankester, M.A., LL.D., F.R.S., 
Jodrell Professor of Zoology 
in University College, London. 
With Plate VIL. 
THE investigation of the nature of the colouring matters 
which occur in different organisms, has always appeared to me 
one of especial importance, leading us, on the one hand, into a 
remarkable region of physiological phenomena, and on the 
other hand, helping us to trace to their true physical causes 
some of the most beautiful and at the same time most puzzling 
of organic developments. The chemical and functional cha- 
racteristics of pigment-compounds are daily becoming better 
understood, and at the same time we are obtaining some 
notion of the way in which nature has here and there 
taken hold of the accidental non-significant property of colour 
in a by-product of the organism’s chemical factory, and has 
assigned to the pigment a high position of importance as an 
ornament, a protective, or a lure. 
In order to understand thoroughly the history of colour in 
the organic world we cannot afford to leave any case unex- 
amined. The green colouring of Oysters some years ago 
attracted my attention because it was asserted that the colour 
of such Oysters was due to the taking up of copper from the 
seawater, brought there by the proximity of old copper mines 
or of copper-bottomed ships. Such a cause of green colora- 
tion in animals would have been, were it substantiated, suffi- 
ciently remarkable, both as a physiological fact and as a 
hitherto unrecognised mode of organic coloration, viz. by 
