332 UNITY AND DIVERSITY IN BIOCHEMISTRY 



on the fibrinogen of the plasma. The various visible stages of this coagula- 

 tion show differences reflecting variations in the underlying chemical 

 phenomena. 



The first type of coagulation is characterized by the development around 

 the coagulocytes of islands of coagulating material and the extension of the 

 process to wider areas by the subsequent organization of this coagulum 

 into a network. In a second type, the coagulocytes extrude threadlike 

 pseudopodial extensions which form networks of varying complexity and 

 on which veils of coagulated plasma often appear. 



Orthoptera and Dermaptera are uniform in showing coagulation of the 

 first type. The same type is found among Hemiptera, in the family Nepidae, 

 the other families of the order lacking the ability to coagulate. The second 

 type is found in all the Lepidoptera. 



Other biochemical characters are peculiar to one or other order of insects. 

 The plasma inorganic bases of Lepidoptera are characteristic in that there 

 is a high percentage of magnesium and potassium and a low percentage 

 of sodium. 



Within the order Lepidotera, certain biochemical characters are typical 

 of certain sub-divisions of the order as has been shown by E. B. Ford in 

 his extensive studies on the wing pigments of butterflies. 



The interest of comparative biochemistry springs from the fact that it is 

 an extension of, and a support to, taxonomy, and thus it becomes possible 

 to connect the study of biochemical diversity and the treasure of accumu- 

 lated knowledge obtained by naturalists over several centuries. 



REFERENCES 



Fogg, C. E. (1953). The Metabolism of Algae. Methuen, London. 

 Florkin, Marcel. (1944) L' ivolution biochimique. Masson, Paris. 

 Florkin, Marcel. (1952). Caracteres biochimiques, des categories supraspecifiques 



de la systematique animale. Ann. Soc. Roy. Zool. Belg., 83, 111-130. 

 Harris, H. (1953). An Introduction to Human Biochemical Genetics. Cambridge 



Univ. Press, London. 

 Haslewood, G. a. D. (1955). Recent development in our knowledge of bile salts. 



Physiol Rev., 35, 178-196. 

 Klein, G. (Editor). Handbuch der Pflanzenanalyse. Springer, Vienna, 1931-1933. 

 MoLiscH, Hans (1933). Pflanzenchemie und Pflanzenwerzvandschaft. Fischer, Jena. 

 Williams, R. J. (1956). Biochemical Individuality . Wiley, New York. 



