10 THE PHYSIOLOGY OF EARTHWORMS 



hand, has a molecular length of 1700 A which is very similar 

 to that of insect striated muscle. It is suggested that the degree of 

 polymerization of myosin B is less than that of striated muscle, thus 

 accounting for the shorter molecular length. It is not yet known 

 whether actin is involved in the polymer formation as is the case 

 in vertebrates (Marnyama and Kominz, 1959). 



Pigmentation 



The outer layer or integument of some species of earthworm is 

 often heavily pigmented, a purple-brown substance being deposited 

 in the tissues throughout life (Stephenson, 1930). This pigment is 

 easily extractable from the integument and in solution exhibits a 

 fine red fluorescence under ultra-violet illumination. 



In 1886 MacMunn identified this red fluorescent compound as a 

 porphyrin and suggested that, in common with pigments obtained 

 from Asterias ruhens, Limax flavus and Arion ater this substance 

 was haematoporphyrin, a breakdown product of haemoglobin. 

 This opinion was supported by Kobayashi (1928) who isolated 

 20 mg of porphyrin hydrochloride from 21 kg of E. foetida. The 

 absorption spectrum of this pure material had peaks at 518, 

 530, 559 and 607 m/x (in acid alcohol) and 502, 547, 583 and 622 

 m/x (in alkaline alcohol). Kobayashi considered this to be very 

 similar to the spectrum of haematoporphyrin. 



Dhere (1932) on the other hand, found that the pigment is 

 soluble in pyridine to give a red fluorescent solution having a 

 spectral emission under u.v. that was identical to protoporphyrin. 

 Fischer isolated a specimen of this material and identified it as 

 Kammerer's Porphyrin, a substance now known to be the same as 

 protoporphyrin (see Vannotti, 1954). 



Haematoporphyrin is now known to be absent in nature, being 

 found only in laboratory degradations of haemoglobin. The 

 opinions of MacMunn (1886) with regard to the identity of 

 pigments in Arion, Asterias and Limax have been shown to be 

 erroneous by modern techniques (Kennedy, 1959; Kennedy and 

 Vevers, 1953), and his ideas on Lwnhricus were also wrong, as 

 indicated by Dhere and Fischer and recently confirmed by 

 chromatography by Lave rack (1960a). 



Laverack (1960a) found that a red fluorescent pigment of the 

 body wall was extracted by ether containing acetic acid, giving a 



