142 PHYSIOLOGY OF THE INVERTEBRATA. 



or exposed for a long time to air, it decomposes spontaneously, 

 part of the albuminoid remaining in solution and part 

 separating in a white, flocculent form. This albuminoid is 

 entirely distinct from hsemocyanin, and has been called 

 hgemorhodin. If the blood is concentrated in- vmuo and 

 heated, it becomes opalescent at 58° C, and coagulates 

 completely at about 70° 0. 



The blood of Aplysia punctata is quite different, and 

 contains 1.77 per cent, of a perfectly colourless hsemocyanin 

 which is not affected by air, and coagulates at about y6° C. 

 This albuminoid probably plays no part in the absorption of 

 oxygen. 



In the Gasteropoda, Cephalopoda, as well as in the Crustacea 

 and Arachnida, the function of respiration is brought about 

 by an albuminoid substance analogous to haemoglobin, but 

 contains copper instead of iron. This substance, which 

 Fredericq* named hsemocyanin, combines with oxygen, form- 

 ing a very unstable combination. 



The blue colouring matter of the blood of Octopus vulgaris 

 is due to the absorption of oxygen, for if the blood is placed 

 in vacuo it loses its colour, but regains it iii the presence of 

 air or oxygen. Hsemocyanin occurs in the arteries of the 

 living Oct(ypus. 



Krukenbergt examined the blood of Sepia officinalis, 

 Carcinus Tiicenas, Homarus vulgaris, Squilla mantis, as well 

 as other species of the Mollusca and Crustacea, and observed 

 that the blood becomes blue by shaking with oxygen or air ; 

 and that the blue colour disappears more or less with carbonic 

 anhydride. " Krukenberg also found great differences in the 

 blood of individual Gasteropod Molluscs, which led him to 

 assume that perhaps the oxygen in such cases is in a firmer 

 combination with the hEemocyanin than is the case in Crabs 

 and Cephalopods. He also made the interesting observation 



* Archives de Zoologie Expirimentale, 1878 ; see also Fredericq's La 

 Lutte pour VExistetice, p. 84. 

 f Vergleieh. Physiol. Studien, ist E., 3 Abh., 1S80, S. 72. 



