426 MARION I. NBWBIGIN. 



described iu Bonellia, makes the characters of the green pig- 

 ment of Thalassema a question of some interest. I do not 

 propose to repeat here my notes on the subject (see Professor 

 Herdman's paper), but wish merely to point to the special 

 differences from bonellin. The pigment is greenish blue in 

 tint, the blue being accentuated by acid — a point I did not at 

 first notice, but which is of some interest. It is readily 

 soluble in formalin or in water, and the residue after the eva- 

 poration of the formalin is soluble in alcohol, although Pro- 

 fessor Herdman did not find that the worm itself yielded a 

 coloured solution when placed in alcohol ; this may, however, 

 have been due to the small amount of pigment present. None 

 of the solutions are fluorescent, and the spectrum shows a 

 single band at about X 617 (cf. the band at X 614 in alkaline 

 bonellin). If we compare these characters with those given 

 previously, as tending to characterise the derivatives of chseto- 

 pterin, we find that the solubility in water, the loss of fluor- 

 escence, the definiteness of colour, the simple spectrum, all 

 reappear. It seems to me not improbable that thalassemin, 

 which is apparently common among the Echiuridte, is a deri- 

 vative of a pigment allied to chtetopterin, and that it quite 

 possibly occurs in Bonellia itself, in addition to a chseto- 

 pterin-like pigment.^ 



(3) Other Green Pigments. 



In view of the simultaneous occurrence in the Echiuridte of 

 an apparently complex pigment like bonellin and a simple one 

 like thalassemin, it is interesting to inquire whether similar 

 simple pigments do not occur in association with enterochlo- 

 rophyll and chsetopterin. There is one marked case of this 

 kind which does not appear to have been yet described. 



The tortoiseshell limpet, Acmsea testudinalis, so common 



^ 111 connection witli thalassemia it "may be well to mention that I find that 

 the green reaction with nitric acid described in my previous notes is an error. 

 The reaction is the result of the action of impure nitric acid on alcohol, and 

 has no connection with the pigment. (See DasLre et Tloresco, ' C. 11. Soc. d. 

 Biol.,' X, 1898.) 



