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observe from what part especially the development of gas 
takes place. The blood-corpuscles may in this way be 
demonstrated as being the part of vertebrate blood from 
which oxygen is eliminated in the guaiacum experiment. 
When guaiacum is used a porcelain plate is preferable to 
blotting-paper for the reception of the solution, since it shows 
any change in the colour more clearly than the paper does. 
Reduced Cruorin — that is, deoxodized O, Hb — gives the 
evolution of gas and the coloration of guaiacum as readily as 
does scarlet Cruorin or O, Hb ; so does Haematin, and so does 
Dr. Thudichum’s Cruentin. Hence we cannot conclude at 
once that it is oxygen held as in O, Hb which is liberated by 
the loose oxygen of the hydrogen peroxide. The action has 
to be further inquired into and explained. 
Distribution of Hcemoglobin among Invertebrata. — In addi- 
tion to Planorbis, Chironomus, and Annelida, I have found 
haemoglobin lately in insect-larvae, and, what is more inte- 
resting, in a Crustacean, viz., the Phyllopod — Branchipus 
stagnalis. In this latter form it exists in such small quan- 
tity as to give but a faint yellow-pink tint to the creature ; its 
presence could never be even suspected by examination with 
the unaided eye. The spectroscope at once demonstrates, 
beyond the possibility of doubt, the presence of the Haemo- 
globin, identical with that found in man. The red colour of 
many Entomostraca, and of the tail of the male Branchipus , 
is not due to Haemoglobin, though I believe it exists in other 
Entomostraca, of a pinkish hue. My friend, Dr. Edouard 
Van Beneden, has discovered a red vascular fluid in certain 
Crustacea, which he is about to examine with the spectro- 
scope, and, I have no doubt, will prove the presence of 
Haemoglobin. 
It might be supposed that Hb is present in very small 
quantity in the colourless fluids of Invertebrata -which give 
the guaiacum reaction, and this idea is rather favoured by the 
small quantity present in Branchipus. The spectroscope 
would, however, detect a much smaller per-centage than is 
there present ; and there seems every reason to believe, from 
the intensity of the action in some cases, as, e.g., in the peri- 
visceral fluid of Sabella and of Lumbricus, that it is not in 
these cases dependent on a small quantity of red Haemoglobin, 
but on a colourless allied body, comparable to the green allied 
body Chlorocruorin. 
I may here mention that I have found a species of Enchy - 
treeus — a genus of Lumbricoid worms supposed to have a 
colourless vacular fluid (Carus gives ‘ Blut farbloss’ as a cha- 
racter of the family) — in which the vascular fluid was quite 
