ON THE EVOLUTION OF HEMOGLOBIN. 81 



but if it is really formed in the liver, it seems probable that 

 it must to some small extent pass into the blood, or else it 

 could scarcely find its way into the other organs. I have 

 also met with it in Planorbis corneus, in the liver, and in 

 another glandular organ with a granular structure ; but the 

 most important coloured substance in the animal is a modi- 

 fication of haemoglobin dissolved in the blood. This com- 

 pound is of such a remarkable character as to claim very 

 special attention. 



In its natural state this red blood of Planorbis gives so 

 nearly the same spectrum as that of the haemoglobin of 

 human blood, that it was regarded as the same substance by 

 Ray Lankester.^ There is, in fact, no difference in general 

 character, and, like the normal kind, when deoxidized, the 

 two bands disappear and are replaced by a broad band ; but 

 yet on careful comparison it may easily be seen that the two 

 well-marked bands of the oxidized state lie nearer to the 

 blue end than in the spectrum of normal haemoglobin, as will 

 be seen from the following table : — 



Centres of the bands. 



Normal hsemoglobin 581 . 545 



Planorbis 578 . 542^ 



Even if there be a little doubt as to the exact wave-lengths 

 true to a millionth of a millemeter, there is none as to the 

 fact of the bands being nearer to the blue end by a wave- 

 length of 2^ or 3 millionths. This difference cannot be 

 due to any difference in the physical state of the substance, 

 since in both cases it was perfectly dissolved in a relatively 

 large quantity of water. It is rather of such a character as 

 would result from the substitution of one kind of albumenoid 

 for another in combination with the same modification of 

 hcematin, into which both are decomposed when boiled with 

 ammonia or decomposed by acids. This conclusion is made 

 almost certain by the difference in the temperature at which 

 they are decomposd by the coagulation of the albumenoid. 

 The red aqueous solution of Planorbis haemoglobin slowly 

 turns brown, and is decomposed into haematin at the compara- 

 tively low temperature of 45° C, and is rapidly changed and 

 coagulated at 49°; whereas in the case of a similar solution 

 of human haemoglobin, similar changes do not occur until the 

 temperature is raised to 65° and 69°. There is thus a dif- 

 ference of about 20° C. in the temperature at which the albu- 

 menoids coagulate ; and this fact taken in conjunction Avith 

 the character of the spectra appears to me very satisfactory 

 evidence of a well-marked difference in the albumenous con- 

 ^ ' Proc. of Roy. Soc.,' vol. xxi, p. 70. 



NEW SEU. VOL. XVI. F 



