DYNAMICS OF MORPHOGENESIS 205 



features more distinctly characteristic of the different reagents. 

 The sHght differences of this sort in Planaria are, I believe, good 

 indications of the low physiological specification of the tissues. 



V. SUMMARY 



1. In Planaria and in many other forms in which there is no 

 highly speciaKzed skeletal or connective tissue, death is followed 

 within a short time, varying from a few minutes to a few hours, 

 by disintegration. This fact makes it possible to determine with 

 some degree of accuracy the time of death of animals, regions of 

 the body or pieces. 



2. Experiments with stimulated and unstimulated animals, 

 with animals at different temperatures, with old and young 

 animals, with animals in different nutritive condition and with 

 pieces of different size, from different regions of the body and 

 under different conditions demonstrate the existence of a relation 

 between the length of life (physiological resistance) of the animals 

 or pieces in KCN, alcohol and various other anesthetics and the 

 rate of the metabolic reactions or certain of them, probably the 

 oxidations. 



3. In relatively high concentrations, in which the maximum 

 length of life is only a few hours, the length of hfe (resistance) 

 varies inversely as the rate of reaction in the animals or pieces. 

 The higher the rate of reaction, the earlier does disintegration 

 begin and the more rapidly it proceeds and vice versa. This is 

 the direct method of comparing rates of reaction. 



4. In relatively low concentrations, in which the animals 

 remain alive for days or weeks and in which a greater or less 

 degree of acclimatization occurs, the length of life (resistance) 

 varies directly as the rate of reaction, except in certain cases 

 where incidental factors contribute to the result. The higher the 

 rate of reaction in the animal the more complete the acclimatiza- 

 zation, at least in most cases, and the greater the length of life. 

 This is the indirect method. 



5. With concentrations between these two extremes the results 

 differ according to the concentration of the reagent used and the 



