60 ANIMAL COLOURING MATTERS EXAMINED AT THE 



not so well marked in the case of tlie alcohol solution. Water 

 extracted from Lepralia a little reddish yellow colouring matter, 

 showing some shading at the blue end of green, and glycerine a little 

 yellow. The acetic acid solution was brownish yellow, and in deep 

 layers absorbed all the spectrum except the red, while in a tbin 

 layer it showed a band at the blue end of green.* 



I formerly found chlorophyll in Flustra foliacea, where it is 

 evidently due to the presence of the brown bodies, the remains of 

 the atrophied Zooids. 



The only mollusc which I had time to examine roughly was Doris, 

 but in this I found evidence of the presence of a hfemochromogen- 

 like spectrum, resembling exactly that of the pigment which I have 

 named enteroheematin, and which Sorby found in several snails and 

 slugs, and I found in Patella and Astacus.f This pigment is, as I 

 have shown, connected with the histohsematins, which have a very 

 wide distribution throughout the animal kingdom. 



Remarks. — It was evident to me that every pigment which I met 

 with, in this somewhat rough and unfinished series of observations, 

 could be classified under groups which have already been described 

 by others and myself ; but they are not on that account the less inter- 

 esting, as the distribution of these pigments is of great importance. 



To morphologists the study of animal chromatology may seem 

 trivial, but the pigments are of great importance from a physiolo- 

 gical point of view, and the discovery of haemoglobin, haemocyanin, 

 the histohsematins, echinochrome, and other respiratory colouring 

 matters, has thrown much light on the respiratory processes in animals. 



With regard to the lipochromes, it is difiicult to understand what 

 role they play. I cannot think that they can be of much use in 

 respiration, as they are unaffected by oxidizing and reducing 

 agents as are other respiratory substances. And I therefore differ 

 from Merejkowski with regard to tetronerythrin being respiratory, as 

 it — as I said before — has been shown to be a lipochrome. It is 

 significant that such widely separated structures as the eye-spot of 

 a starfish and the rods of the Vertebrate eye should each yield 

 lipochromes ; it would seem that in such cases they are concerned 

 in the absorption of light-rays. J Probably their simple chemical 

 constitution, as they all consist of only three elements, carbon, 

 h.ydrogen, and oxygen, has been taken advantage of for such pur- 

 poses, as they can be built up with the minimum expenditure of 

 energy. It is interesting also to note that they have a very strong 

 absorptive power for the violet end of the spectrum. 



* Cf. Krukenberg, Verg. physiol. Stud., 2 Reihe, 3 Abth., S. 29. 



t Philos. Trans., Pt. i, 1886, p. 239, and Ibid., p. 268. 



X Cf . Sir J. Lubbock in The Senses of Animals, Internat. Sci. Series, p. 3, et seq. 



