236 



Colouring Matters in Diazona violacea. 



on the extendi', and not throughout the mass of the colony. It may also be 

 remarked that a minute quantity of the pigment causes an intense coloration 

 of its solvents, so much so, that if all the violet colouring matter in a colony 

 was in solution during life the colour of the organism would almost certainly 

 be a bright blue, not yellow green, as it would entirely mask the yellow of 

 the chlorophyll body. 



The non-production of violet colour in the formaldehyde-preserved 

 specimens is what one would expect from an indigo derivative, for the 

 reducing action of the aldehyde would certainly produce colourless indigo- 

 white derivatives, if indeed the whole molecule was not split up. 



The recorded phenomena can, however, be explained if we suppose that in 

 the healthy animal the pigment is present dissolved in the pigment cells in 

 its reduced condition as a chromogen. Owing to its natural tendency to 

 oxidation the animal by maintaining it reduced could use it as an oxygen 

 carrier, and, since the only available oxygen is in the surrounding water, its 

 presence would only be expected on the exterior of the colony, though the 

 green-yellow chlorophyll-like pigment is present throughout its mass. As 

 soon as the animal became moribund or unhealthy metabolic processes would 

 change and oxidation would begin, with the consequent production of colour. 

 In the dead animal oxidation would be complete, and the colourless body 

 converted into the violet pigment. The same change would occur in alcohol, 

 which by killing the animal would allow oxidation to proceed rapidly. 



The colour results no doubt from the action of an oxydase, which in the 

 formaldehyde-preserved specimens would be destroyed, and hence no colour 

 would result. Until it is possible to experiment with living colonies one 

 cannot express a definite view, but it appears more probable that some such 

 series of changes as is outlined above takes place, rather than that the body 

 in its fully oxidised condition is present in solution in the pigment cells of the 

 live auimal. 



With only preserved colonies available it is not possible to prosecute further 

 this enquiry as to these green and violet pigments or to express any opinion 

 as to their possible relationship, as regards function in the organism, to those 

 found in Bonellia and various Mollusca. 



In conclusion my thanks are due to Prof. Herdman for providing several 

 complete colonies of Diazona and the green alcoholic solutions obtained 

 directly from the living organisms, and for suggesting to me that a chemical 

 investigation might throw further light on the colour relations of the violet 



Diazona violacea and the green condition known as Syntethys hebridicus. 



