The Collaborative International Dictionary of English v.0.48:

Haemacyanin \H[ae]m`a*cy"a*nin\ (-s[imac]"[.a]*n[i^]n), n.
   [H[ae]ma- + Gr. ky`anos a dark blue substance.] (Physiol.
   Chem.)
   A substance found in the blood of the octopus, which gives to
   it its blue color.
   [1913 Webster]

   Note: When deprived of oxygen it is colorless, but becomes
         quickly blue in contact with oxygen, and is then
         generally called oxyh[ae]macyanin. A similar blue
         coloring matter has been detected in small quantity in
         the blood of other animals and in the bile.
         [1913 Webster]