294 Proceedings of Royal Society of Edinburgh. [sess. 
This substance (as is well known) forms an oxygenised combina- 
tion which is very unstable, and which is carried by the blood 
across the tissues of the animal, and is there dissociated, yielding 
its oxygen to the elements of those tissues which require it. 
Professor Ray Lankester discovered that in some of the Annelida 
the haemoglobin is replaced by a green-colouring matter — chloro- 
cruorin ; but in the majority of these animals haemoglobin is present, 
which the author has proved to be similar in composition to that 
present in the higher animals. Concerning this point, the author 
obtained the blood of 500 earthworms ( Lumbricus terrestris) which 
was treated with benzene. The mixture (in solution) was allowed 
to stand for twenty-four hours at 0° C., when it separated into two 
distinct layers. The one containing the colouring matter was now 
separated from the other ; and about one-sixth its volume of pure 
absolute alcohol was added. After filtration the alcoholic extract 
was exposed to - 12° C., when red crystals were obtained. These 
crystals yielded the following results on analysis : — 
Blood of Lumbricus. 
Blood of 
Dog. 
I. 
II. 
III. 
Carbon, 
53*91 
53-86 
52-85 
Hydrogen, . 
7-02 
7-10 
7-32 
Nitrogen, . . . 
16-17 
Sulphur, 
6*41 
6*37 
0-39 
Iron, .... 
6-39 
0-43 
Oxygen, . 
21-84 
The above analyses prove that the colouring matter of the blood 
of Lumbricus is comparable chemically to that of a Vertebrate 
animal — like the dog. The spectrum of this colouring matter is 
identical with that of Vertebrate haemoglobin. 
Although haemoglobin is present in the blood of certain Inverte- 
brates, the chief constituent in the blood of the majority of these 
animals is haemocyanin — a compound analogous to haemoglobin, but 
containing copper instead of iron.* 
* Concerning the coagulation of the blood of certain Invertebrates, the 
reader is referred to the important paper by Drs J. B. Haycraft and E. W. 
Carlier in the Proc. Roy. Soc. Edin ., vol. xv., p. 423. 
