2IO J, S. NICHOLAS 



ited by some factor other than the concentration of cytochrome oxidase. 

 By the application of the heterauxetic equations the relative growth rates 

 of cytochrome oxidase and cholinesterase have been determined and the 

 individual character of these processes of biochemical differentiation 

 shown. 



The evidence in the work of Sawyer, Boell, and Shen shows clearly 

 the place which the development of the enzyme plays in the functional 

 organizational development. The fact that the enzymes have different 

 developmental rates indicates the significance which they have in the 

 general growth properties of the embryo and, what is still more im- 

 portant, how they are correlated with the specific parts of differentiation. 

 The interesting problems of the changes in the substrates from which 

 these materials are formed still await solution and will undoubtedly 

 form an important phase of the understanding of organization. 



Regeneration 



The problems of organization are not limited to those which can be 

 attacked with embryonic material, for in every regenerating structure 

 there is a new organization involving both growth and differentiation in 

 the attainment of the new structure. It is impossible here to cover the 

 wealth of vertebrate and invertebrate material which yields information 

 on various phases of the problem of morphogenesis during regeneration. 

 One example can be cited in order to show the changing attack in this 

 field, the relation of the nervous system to limb regeneration. 



Schotte ('23, '26) on the basis of a great deal of work in the am- 

 phibian nerves came to the conclusion that some elements of the nervous 

 system were necessary in order that regeneration should be initiated and 

 completed. This work has been continued (Schotte and Butler ('41), 

 Butler and Schotte ('41), and Schotte and Butler ('44)). They have 

 studied the various phases of the formation of the blastema and the way 

 in which each is affected by the presence of nervous system. The nerves 

 seem to be necessary for the dedifferentiation phase leading to blastema 

 formation and also in the transformation of the blastema into a regen- 

 erate with morphogenetic determination. After morphogenetic deter- 

 mination is established, the presence of nerves is no longer necessary for 

 subsequent growth and differentiation. 



The research referred to above seems to answer one of the problems 

 of regenerative organization in that it solves the particular role of nerv- 

 ous tissue in blastema organization. That there are other factors still 



