378 W. A. HERDMAN. 



that they are really of the nature of chlorophyll. They are apparently useless 

 substances, eliminated either by the gut or by the skin, or sometimes by both. 



"M. T. Newbigin." 



Professor Sherrington and Dr. Noel Paton, as is shown 

 above, differ somewhat in their localisation of the absorption 

 band, but that may possibly be due to a change caused by the 

 evaporation, to about one half, of the formol solution. 



The result appears to be that this substance, which may be 

 appropriately named '' Thalassemin," is a remarkable and appa- 

 rently unknown pigment, which is not allied to haemoglobin nor 

 to chlorophyll. It is not a respiratory pigment, and is apparently 

 nearer to " bonellein," described by Dr. Sorby in 1875,^ from 

 the Gephyrean Bonellia viridis, than to any other known 

 pigment ; but differs markedly from bonellein in several re- 

 spects, besides having a single in place of a multiple band, and 

 so cannot be identical with that substance. Possibly thalassemin 

 is more closely related to the green pigment of Hamingia. 



The chart showing the spectral characters drawn up by 

 Professor Sherrington is given in PL 28, fig. 35. I may add 

 ^that this pigment is so intense that even in the case of the 

 specimen from which the formol solution referred to above 

 had been extracted, the green colour is still distinctly visible 

 in the pigment masses of the dermis in thin sections (about 

 8 ju) under Zeiss's -^ oil immersion. 



Systematic Position. 



In 1883 Professor Lankester gave an account of some 

 specimens of Hamingia arctica, Kor. and Dan., from the 

 Hardauger Fjord, and discussed fully the relations of the 

 genus Hamingia to Thalassema and Bonellia. He con- 

 sidered Horst^s H. glacial is to be the same as Koren and 

 Danielssen's H. arctica; and from the additional specimens 

 he and Canon Norman dredged in the south of Norway he 

 was able to add considerably to our knowledge of the struc- 

 ture of this form, and of the differences between it and the 



' ' Quart. Journ. Micros. Sci.,' N. S., vol. xv, p. 166. 



