228 



Dr. A. Holt. Colouring Matters in the 



in so far that the general absorption towards the violet begins at almost 

 the same point, and that there is a very definite band in the orange red. 

 The two spectra are shown in the accompanying figure, where their points 

 of agreement and disagreement are more immediately visible. 



In 1875, Sorby* obtained a green alcoholic solution from the Gephyrean 

 worm Bonellia viridis, which, when examined spectroscopically, gave an 

 absorption spectrum which also resembled chlorophyll in some respects. 

 In neutral solution there was a very pronounced band at X — 636 yu/* and 

 distinct bands at X = 587, 520, and 490 ^/a, but he does not record any 

 general absorption for A.<470// / i6. His spectrum (" bonelleine ") is also 

 reproduced in the figure for the sake of comparison. 



Judging solely from these observations, it appears very probable that 'the 

 green solutions from Diazona and Bonellia contain either chlorophyll (for 

 chlorophylls from different sources have not identical spectra), or some 

 closely related chlorophyll body. 



On cutting a violet, alcohol-preserved specimen of Diazona in two, it was 

 found that the tint only extended a short way (about 1 cm.) beneath the 

 surface, by far the larger mass of the colony (perhaps 20 cm. across) 

 remaining a pale greenish yellow. The coloured outer portion of a specimen 

 was therefore removed, and extracted with absolute alcohol. A blue-green 

 solution was slowly obtained, but only a very minute portion of the violet 

 pigment appeared to pass into solution. On cooling the alcoholic extract 

 the blue-green colour became both paler and more yellow, though the original 

 tint was restored on reheating, while after standing in the cold for some 

 days a very small quantity of a substauce having a violet tint identical 

 with that observed in the outer portions of the colony was precipitated, the 

 solution from which it had separated being now yellow-green. Extraction 

 of the inner portions of a colony with absolute alcohol gave a solution of an 

 almost pure yellow tint, scarcely any trace of green being detectable by the 

 eye. No change took place either on cooling or after standing for some time. 



The spectrum of the blue-green solution appeared to be similar to that 

 already described, there being absorption in the red, and general absorption in 

 the blue and violet, but the yellow solution from the interior of the colony gave 

 no distinctive band, but only a general absorption of the more refracted rays. 



On standing for several days these solutions became somewhat paler in tint, 

 but attempts to concentrate the colour by distilling off the alcohol resulted in 

 such turbidity that spectroscopic observations were impossible. The original 

 green solution obtained from the 1912 specimens has scarcely altered in tint 

 (April, 1914),' but on concentration it also becomes turbid. 



* ' Quart. Journ. Microsc. Sci.,' vol. 15, p. 167. 



