AND THE HEBEIDEAN DIAZOXA VIOLACEA. 169' 



Aceorclmg- to this nomenclature our ' Buna ' specimens would fall into 

 the first variety, the name of which I would prefer to write as D'lazona 

 violacea, Savigny, variety Jiehridica, Forb. & Goods. 



Turning now to the colour of the colony as a whole^ and to the change of 

 colour that has been described, we find that the curious point about the 

 colour of this animal is that, whereas British specimens are green when alive 

 and become violet when preserved in spirit, Mediterranean specimens are 

 apparently sometimes violet and sometimes green, and the latter do not 

 always change their colour when treated with alcohol. Professor E,. Dohrn, 

 Director of the Zoological Station at Naples, has kindly sent me a pale green 

 Diazona violacea preserved in alcohol, and he informs me that both green 

 and violet-coloured specimens have been obtained from time to time in the 

 neighbourhood of Naples. He states that it has not been noticed in their 

 preservation department at the Zoological Station that any change of colour 

 takes place on adding alcohol ; but he adds in his letter that he remembers, 

 to have noticed that the green Diazona becomes of a bluish colour when 

 injured *. 



It is remarkable that my large violet-coloured ' Runa ' colony still con- 

 tinues after four months^ preservation to give out the green pigment, as 

 three successive changes of spirit have now been coloured by it. The violet 

 jDigment of the preserved specimen, however, seems to be insoluble, as 

 fragments so coloured have been kept in absolute alcohol, in chloroform, in 

 bisulphide of carbon, and in xylol for weeks without showing any change 

 in tint. 



The brilliant green solution which this Hebridean specimen has given 

 with alcohol has been examined spectroscopically for me by Dr. Alfred Holt, 

 Reader in Physical Chemistry in the University of Liverpool, and he has 

 shown me that the pigment is not chlorophyll — as might have been supposed 

 at first — but has a characteristic absorption band in the orange intermediate 

 in position between the band given by sodium and that of chlorophyll. The 

 ])osition of this band in Angstrom units is 6200; while chlorophyll gives a 

 band at G550, and bonelleine, described by Sorby in 1875 from the green 

 Gephyrean worm Bonellia viridis, has a corresponding band in the orange 

 at 6430. In chlorophyll there is much greater absorption at the blue end 

 of the spectrum, and in " syntethine," as observed, there is almost an 

 identical effect, while in bonelleine there is a well-marked band in the blue 

 and relatively less absorption in the indigo and violet. 



The " Syntethys" pigment (we do not know yet whether it can be obtained 

 also from the Diazona that is violet wheii living) does not go purple with 

 acids, and therefore cannot be bonelleine. Acids or alkalies turn it some- 



* F. Lahille states (1890) that specimens at Banyuls kept in aquaria degenerate; and that 

 their pale yellowish colour becomes bluish or yiolet. 



