170 PROF. W. A. HERDMAN ON FDNICULINA QUAURANGULARIS 



what yellowish, and the colour is not restored on neutralisation. No distinct 

 bands-are shown in acids or alkaline solutions. Possibly our substance and 

 bonelleine belong to the same natural group (what Sorby called a " genus ") 

 of pigments. Dr. Holt has kindly supplied me with a diagram (fig. 2) 



Fig. 2. 



Jooo iiooo Sooo /,(3oo 



"■ Syntethine." 



Chlorophyll. 



Bonelleine. 



showing the spectrum of: the new pigment — to which the name "syntethine '^ 

 may be appropriately applied — compared with those of bonelleine and of 

 chlorophyll. 



The violet of the large ' Euna ' colony in its present condition is the 

 complementary colour to the green which has been dissolved out of it, so 

 that when the colony is submerged in the solution it ap[)oars to lose at once 

 its brilliant colour and become dull grey. The question then arises — was the 

 violet pigment present, masked by the green, when the animal was living ; 

 or has chemical action taken place, possibly due to dehydration by the 

 alcohol, which, while dissolving out the green, caused the precipitation of 

 another previously less conspicuous pigment in the present oi)aque violet form ; 

 or, are the green and the violet two forms of the same pigment partly dis- 

 solved out in the green form and partly precipitated as the insoluble violet ? 



Histologically the violet colour is due to minute opaque granules closely 

 placed in the spherical pigment cells with which the test is found to be 

 crowded (see PI. 14. fig. 3). Similar opaque green pigment cells are visible 

 in abundance in the test of the 'Puna'' specimens which are preserved in 

 formalin (PI. 14. fig. 1). 



It is evident that the little we know of this pigment does not yet throw 

 any light upon the curious colour changes in T^/arona, and fails as completely 

 as the structural characters to aff'ord any evidence of specific distinction 

 between the Mediterranean and the Hebridean forms. " Nimium ne crede 

 colori '"' may be a sound aphorism for the systematist in some groups, but 

 still colour does mean something and may mean a great deal from the 

 physiological point of view. 



The colony of Diazona is known to undergo remarkable degenerative and 



