268 DR. 0. A. MAC MUNN ON MYOH.EMATIN AND THE HIST0HH3 MATINS. 
derived great assistance by the use of an instrument provided with shutters in the 
eye-piece by means of which any portion of the spectrum can be cut off, which was 
made by Adam Hilger. When an object is examined in the chemical spectroscope it 
has to be illuminated by a bull’s-eye condenser placed between it and the light-source. 
Animals Examined. —My observations have been confined necessarily to such 
animals as can be procured in an inland place, but the number examined is sufficient 
to prove the wide distribution and importance of the pigments to be described. Had 
my opportunities been greater the results would doubtless have been more important. 
Among invertebrates various mollusca, echinoderms, arthropods, and some worms 
have been examined ; the results of the examination of actiniae have been already 
communicated to the Royal Society. Among vertebrates various reptiles, amphi¬ 
bians, fishes, birds, and mammals have been examined, and the results obtained show 
that there is no essential difference in the spectra of the organs and tissues of 
vertebrates and invertebrates, when the influence of the circulating haemoglobin in 
the former has been eliminated. 
I. The HlSTOHiEMATINS. 
In Dr. Sorby’s paper on the “ Evolution of Haemoglobin”* a remark occurs which 
shows that he had seen a spectrum which is that of a histohaematin. Speaking of 
the haematin first observed by him in the bile of Helix he says :—“ I think it very 
probably does occur in the muscles of the foot and elsewhere,” &c. Here at least a 
previous observer—whose opinion is of great weight owing to his skill in chroma- 
tology—suspected the existence of a haematin-like pigment in the tissues of an animal, 
and believed it to be related to the haematin of the bile of the same animal. Not 
only, however, does a histohaematin occur in an animal whose “ bile ” shows a haemo- 
chromogen-like spectrum, but also in other animals in which no haemochromogen can 
be detected in the “ bile,” and the bands of the respective histohaematins are abso¬ 
lutely identical. Moreover we find the histohaematin spectrum replaced by that of 
a haemochromogen-like spectrum in the solid organs and tissues in individual cases ; 
it is for that reason that I have named these pigments histohaematins. No other 
observers, so far as I know—except Dr. Sorey and myself—have seen, or at least 
have recorded, the occurrence of such a spectrum in the organs or tissues of an animal. 
Histohcematins of Echinodermata. 
The tissues and organs of various echinoderms have been examined, and in most 
of them the appearances differ in no respect from those seen in Uraster rubens. In 
this species the spectra are well marked, and may be taken as typical, their bands 
being very sharp and easily seen. 
If we compare the spectrum of the generative organs of Uraster with that of 
* Quart. Journ. Micros. Soc., vol. XVI., New Series, pp. 77 et seq. 
