ANIMAL CHLOROPHYLL 



351 



been stated MacMunn (1885 c) demonstrated in many actinians 

 the presence of a liaematin-yielding pigment, which was 

 designated as actiniohaematin. Recent investigations have 

 shown that haemoglobin and chlorophyll are similar chemically, 

 each having as a base a substance known as a porphyrin. 

 This derivative is composed of four pyrrol groups in complex 

 linkage. The exact similarity which exists between haemo- 

 globin and chlorophyll may be shown by the following : ^ 



Haemoglobin 

 (by K,C03) 



Haematin ( + proteid) 

 (by acid) 



Chlorophyll a 

 (by alkali) 



phyllins (+ phytol) 

 (by acid) 



(Haemato) porphyrin ( + Fe) 

 (by soda-lime) 



(phyllo) porphyrin (-fMg) 

 (by soda-lime) 



\ 1^ 



' aetioporphyrin " 



Thus haemoglobin, by the loss of a proteid (globin) and its 

 iron, forms a porphyrin ; in the same way chlorophyll a, by 

 the loss of phytol and its magnesium, forms several porphyrins, 

 one of which (phyllo) is spectroscopically and chemically 

 very closely related to haematoporphyrin ; both phyllo- 

 porphyrin and haematoporphyrin by the action of soda-lime 

 give the same substance, aetioporphyrin. From this it seems 

 evident that there is no a priori reason for assuming that the 

 tissues of actinians could not convert chlorophyll into such 

 a substance as actiniohaematin, which is closely related to 

 haemoglobin. The obvious objection is that exchange of 

 metals (iron for magnesium) would make such a transformation 

 impossible. But one should recall that it is a far more simple 



1 The best discussion in English of the chemistry of haematoporphyrin 

 and chlorophyll is that of Phmmer (1915); BayUss (1918) is good, but 

 the standard work is that of Willstatter and Stoll (1913). 



