H. MUNRO FOX 



by H. Fischer and C. von Seemann 2 to differ from protoporphyrin 

 only in one side chain of one of its 4 pyrrol rings, where a vinyl is 

 oxidized to an aldehyde group. This constitution of chlorocruoro- 

 porphyrin was confirmed by H. Fischer and K. O. Deilmann 3 , who 

 synthesized it by the oxidation of one vinyl group of protoporphyrin. 



Oxygen attaches itself to the iron of chlorocruorin in the same 

 numerical atomic ratio as it does to the iron of haemoglobin : two 

 atoms of oxygen to one of iron 4 . Chlorocruorin has a much lower 

 affinity for oxygen than most haemoglobins. At 17°C and /?H 7-7 the 

 chlorocruorin of S. spallanzanii is 50 per cent in the oxy state at an 

 oxygen pressure of 27 mm Hg 5 . At the same temperature and in the 

 absence of carbon dioxide the oxygen pressures for 50 per cent oxy- 

 haemoglobin are 0-6 mm Hg for Chironomus riparius and 3-1 mm Hg 

 for Daphnia magna 6 . These are the highest and one of the lowest oxygen 

 affinities of all blood haemoglobins. The Serpulimorpha are sluggish 

 sessile animals and considering their mode of life they have a surprising 

 quantity of chlorocruorin in their blood ; indeed, the oxygen capacity 

 is greater than that of any other invertebrate blood, whatever its 

 respiratory pigment. While the oxygen affinity of chlorocruorin is 

 low, however, its affinity for carbon monoxide is higher than that of any 

 haemoglobin 7 . 



Until lately it was thought that all species of the group Serpuli- 

 morpha have chlorocruorin in their blood. But this is not the 

 case 8 . I have found chlorocruorin in 21 species of Serpulimorpha, 

 belonging to 15 genera. One of these species is Spirorbis borealis ; 

 but another species in the same genus, namely S. corrugatus, has 

 haemoglobin instead of chlorocruorin in its blood, while a third one, 

 S. militaris, has neither blood pigment. The three species live in the 

 sea in similar situations and one can suggest no functional reason for 

 the differences in respiratory pigment. 



Moreover, in the genus Serpula the blood is greenish brown, not red or 

 green. This is because it contains both chlorocruorin and haemoglobin. 

 Here, for the first time, two respiratory pigments have been found in 

 the blood of one animal. With the spectroscope three absorption 

 bands are seen : a-oxychlorocruorin, with a- and /?-oxyhaemoglobin ; 

 the small /?-band of the former pigment is hidden by a of the latter. 

 Young individuals have more haemoglobin, older ones more chloro- 

 cruorin. Chlorocruorin, present only in two specialized groups of 

 polychaete worms, may be looked upon as a biochemical mutation of 

 haemoglobin. In this case the greater concentration of the latter 

 pigment in young than in older Serpula would be a case of recapitulation. 



There is only one genus in the Serpulimorpha which has a respiratory 

 pigment in a cellular tissue. This is Potamilla, whose muscles are 



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