BIOCHEMICAL ARCHITECTURE 17 



which is present as blood, coelomic fluid and tissue water. Con- 

 siderable interchange of water occurs across the body wall which 

 shows regional variations in permeability. Surprising tolerance to 

 uptake and loss of water is exhibited. 



Details of the chemical composition of the body await further 

 investigation by the most modern analytical techniques. Figures 

 are available for the amounts of protein, fat, carbohydrate and 

 mineral ash, but only one or two studies have given details of the 

 precise biochemical nature of the compounds present. Two recent 

 studies of the subject have shown that the collagen-like cuticle of 

 the earthworm bears resemblances to, but differs from, the colla- 

 gen of vertebrates and that pigmentation is partly due to a mixture 

 of porphyrin compounds. 



Most significant of biochemical results on the structure of 

 earthworms has been the elucidation of the phosphagen compound. 

 This is not arginine phosphate but lombricine. This substance 

 contains the D-serine moiety: the first fully substantiated report of 

 a D-amino acid to be found in the animal kingdom. 



