78 



Mr. E. Ray Lankester on Hemoglobin. [Dec. 12, 



also in the scales of fish and in the skin and hair of mammals, and in 

 the pigments of many Crustaceans, Annelids, Insects, Timicates, and 

 Sponges *. 



From a consideration of the facts stated above with regard to the mode 

 of occurrence and distribution of Haemoglobin in animal organisms, the 

 following general statements may be made, which are in accordance with 

 the now thorough establishment, by chemical investigation, of its peculiar 

 oxygen-carrying property. 



Haemoglobin is irregularly distributed throughout the animal kingdom, 

 being absent entirely only in the lowest groupsf . It may be present in all 

 the representatives of a large group, with but one or two exceptions, or it 

 may be present in one only out of the numerous members of such a 

 group ; or, again, it may be present in one and absent in another species 

 of the same genus. It may occur in corpuscles in the blood, or diffused 

 in the liquor sanguinis, or in the muscular tissue, or in the nerve-tissue. 

 The same apparent capriciousness characterizes its occurrence in tissues 

 as in specific forms. It may be present in one small group of muscles and 

 absent from all the rest of the tissues of the body, or it may occur in one 

 part only of a tissue, histologically identical throughout its distribution in 

 the organism. The apparently arbitrary character of this distribution is 

 to be explained (though only partially) by a reference to the chemical 

 activity of Haemoglobin. "Wherever increased facilities for oxidation are 

 requisite, Haemoglobin may make its appearance in response ; where such 

 facilities can be dispensed with, or are otherwise supplied, Haemoglobin 

 may cease to be developed. 



The Vertebrata and the Annelida possess a blood containing Haemo- 

 globin in correlation with their greater activity as contrasted with the 

 Mollusca, which do not possess such blood. The actively burrowing 

 Solen legumen alone amongst Lamellibranchiate Mollusks, and amongst 

 Gasteropods only Planorhis, respiring the air of stagnant marshes, possess 

 blood containing Haemoglobin. In the former the activity, hi the latter 

 the deficiency of respirable gases are correlated with the exceptional de- 

 velopment of Haemoglobin. But we cannot as yet offer an explanation of 

 the absence of Haemoglobin from the closely allied species of Solen, 

 and from the Lymncei which accompany Planorhis. The Crustaceans 

 Cheiroceplialus and Daphnia, and the larva of Cheironomus, possessing, 

 as exceptions in their classes, Haemoglobin in their blood, inhabit stations 

 where the amount of accessible oxygen must be small (that is to say, 

 stagnant ponds), the last living in putrescent mud ; whilst the possession 



* See Journal of Anatomy and Physiology, 1869-70, p. 119. 



f [Note. Dec. 24th, 1872.] — It is perhaps of some significance that Haemoglobin has 

 only been found in that great group of the animal kingdom which in the course of its 

 development gives rise to a middle layer of blastodermic cells or mesoderm, and in 

 examples from nearly every great branch of this stem. 



