362 JOHN p. ftjlton, jr. 



Little is known concerning the chemical nature of the 

 pigments of opistho branch molluscs ; however, certain observa- 

 tions of Orozier and others are of interest. Crozier reported the 

 presence of manganese in the pigment of C. zebra, though 

 he did not believe that the manganese facilitated respiration, 

 Paladino (1908) detected both magnesium and iron in the 

 pigment of A p 1 y s i a punctata.^ It appears to the writer 

 that Paladino 's observations are of particular importance in 

 their relation to the origin of animal pigments. In the first 

 part of this paper, evidence has been given to show that the 

 pigment haemoglobin is derived from chlorophyll. The chief 

 objection to such a contention is the difiiculty of exchanging 

 the magnesium of chlorophyll for the iron of haemoglobin. 

 It would seem from Paladino 's work that the coloured substance 

 of A. punctata is a pigment which is intermediate between 

 chlorophyll and haemoglobin since it possesses both magnesium 

 and iron. It probably is not entirely justifiable to draw any 

 conclusion until more is known concerning the chemical nature 

 of the molecule to which the iron and magnesium are attached. 

 However, the pigment showed absorption bands which are 

 similar in some respects to those of haemoglobin ; moreover, 

 nitrogen was detected in the molecule. Both of these facts bear 

 evidence that the pigment of A. punctata possesses the 

 same chemical base as haemoglobin. 



The blood of a closely-allied form, x\plysia depilans, 

 has a distinct rose colour, due to the presence of an albuminoid 

 (Cuenot, 1890) which is precipitated by alcohol and acids. 

 The coloration of the body is due in part to the presence of this 

 substance in the epidermal regions. 



(6) The Cephalopods. 



Among the earlier observations on the blood of cephalopods 

 were those of Kouget (1859), who described colom-ed corpuscles 



^ MacMiinn (1899 6) has made a spectroscopic investigation of the pig- 

 ments of Aplysia punctata. He also found (as did Crozier and 

 Paladino) that the pigment is very sensitive to a change from alkalinity to 

 acidity. 



