BIOCHEMICAL ARCHITECTURE 11 



brown solution. The solution fluoresces red, but the body wall still 

 retained a considerable amount of pigment which was not extracted 

 by prolonged ether : acetic acid treatment. It was easily released 

 by methanol : sulphuric acid (Kennedy and Vevers, 1953) to give a 

 red-violet solution which fluoresces intensely. The two fractions 

 obtained show distinctive behaviour on paper and column chroma- 

 tographs but possess the same absorption spectra, having absorp- 

 tion peaks at 503, 541, 576 and 632 m^ (in chloroform solution) 

 and these peaks correspond very closely with those given by 

 authentic protoporphyrin. From this evidence the two pigments 

 have been identified as protoporphyrin and protoporphyrin 

 methyl ester respectively (Fig. 3). Small amounts of a third red 



CH, 



fluorescent substance have also been seen, probably representing 

 an intermediate product. 



These red fluorescent porphyrin compounds are associated with 

 a second pigment, deep brown in colour, which remains unidenti- 

 fied. 



Kalmus, Satchell and Bowen (1955) have described investiga- 

 tions into the composition of a pigment obtained from a green 

 version of Allolobophor a chlorotica. 



Mucus 



A property of many of the cells of the epidermis of earthworms is 

 the secretion of mucus (Fig. 4). This material is copiously produced 

 in response to various noxious stimuli and may act as a buflFer 

 defence system against such stimuli. Although no detailed study has 

 yet been made of the chemical composition of the mucus it is probably 



