ANIMAL CHLOROPHYLL 365 



aiid the pseudohaemal, or blood-vascular fluid. The fluid of the 

 coelom contains corpuscles, and carries food substances derived 

 from the intestine. The blood, on the other hand, functions in 

 respiration and probably has little to do with the transportation 

 of food. The respiratory pigments, therefore, are found in 

 greatest almndance in the blood-vascular system, though they 

 are sometimes met with in coelomic fluid. 



There are four varieties of pigment found in annelid worms : 

 haemoglobin, chlorocruorin, chlorophyll, and the lipochromes. 



Haemoglobin. — In the more primitive annelids, haemo- 

 globin is found dissolved in the blood plasma, the corpuscles 

 themselves being colourless and serving as phagocytes (most 

 chaetopods and Hirudineae ; Lankester, 1872). In the 

 Capitellidae and in Glyceridae the haemoglobin is packed in 

 individual cells. ^ Much more extraordinary, however, is the 

 occurrence of haemoglobin in the nervous chain of Aphrodite 

 aculeata, and as Lankester (1872, p. 79) remarks it is diffi- 

 cult to account for its appearance there as ' we have no know- 

 ledge that this Annelid is remarkable for nervous energy '. 



Annelid haemoglobin (particularly that of Lumbricus 

 t e r r e s t r i s) is almost identical with the respiratory pigment of 

 vertebrates. Griffiths (1892, p. 147) made a detailed chemical 

 analysis of the haemoglobin of Luml)ricus and found that the 

 only considerable discrepancy between it and the haemoglobin 

 of a dog lay in the amount of iron present, there lieing slightly 

 less iron in the pigment of the annelid. 



Concerning the differences found between the various 

 haemoglobins, a statement which Griffiths (1897, p. 101) 

 makes in another work might very aptly be quoted. ' If 

 species have been modified in the course of long eras, the 

 haemoglobins — though fulfilling all the conditions of a true 

 chemical compound — must have become modified step by step 

 with the species. . . . Hence we see that the conception of evolu- 

 tion must necessarily find a place in chemistry, not merely as 



^ In many text-books — Parker and Haswell, Hegner, &c. — it is stated 

 that the haemoglobin of annelid blood is found dissolved in the plasma. 

 Though true for certain species it is quite incorrect as a general statement. 



