PHYSIOLOGY OF THE INVERTEBRATA. 



147 



matter was tlieii separated from the' other ; and about one- 

 sixth of 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 : — 



The above analyses prove that the colouring matter of the 

 blood of Lumhricus is comparable chemically to that of a 

 Vertebrate animal, like the dog.* 



Although hemoglobin is present in the blood of certain 

 Invertebrates, the chief constituent in the blood of the 

 majority of these animals is h^mocyanin, a compound said 

 to be analogous to haemoglobin, but containing copper instead 

 of iron. 



It is well known that " the blood of many Molluscs and 

 Arthropods is of a blue colour after exposure to the air, and 

 this is in most cases due to the presence of haemocyanin." 



(i) The JEchinodermata. — Dr. MacMunnf has examined 

 the blood of Holothuria nigra. It does not contain haemo- 

 globin, but when examined with the spectroscope it strongly 

 absorbed the violet end of the spectrum but gave no bands. 

 The colouring matter of the blood "is soluble in absolute 



* Griffiths in Proc. Roy. Hoc. Edinb., 1891 (June i). 



t Quarterly Jownal of Microneopical Science, vol. 30, p. 60, 



