lotka: discontinuous evolution 5 



grows by autocatakinesis, each new portion added resembling 

 in general character the original stock. 



The third and last type of biological aggregate which we shall 

 note here is seen in its fullest development in connection with the 

 human race. From the moment when man learnt to till the soil, 

 to raise cattle, and so forth, when therefore the crop in the field, 

 the herd upon the pasture grew in synchronism and in controlled 

 proportion with the human population, from that moment man, 

 together with the plant and animal stock raised and nurtured 

 by him, formed one " economic continuum." This again grows 

 by autocatakinesis, and is seen in its most highly developed type 

 in modern civilized man and his agricultural, industrial, commer- 

 cial and political equipment. 



To recapitulate, we have noted the following types of continua: 



1. Physical continua — Phases. 



2. Chemical continua — Elements, Compounds, Associates, Dis- 

 sociates. 



3. Biological continua — (a) Physiological: Kindred-Groups 

 (Species), (b) Sociological: Societies, (c) Economical: Eco- 

 nomic systems. 



A complete discussion of the subject of "Evolution in Discon- 

 tinuous Systems" should, then, cover all those "changes of state," 

 in which any of the types of continua noted in our table are suf- 

 fering changes in character or in mass. It would therefore include 

 the physics of change of state, the whole of physical chemistry, 

 the study of radioactive transformations, and the discussion of 

 certain biological, sociological, and economic questions. 4 I pro- 

 pose to restrict myself here on the one hand to considerations 

 relating to the subject as a whole, as embodied in this introduction, 

 and on the other hand to the treatment of one or two specific 

 examples which have not hitherto received much attention from 

 this point of view. 



A point has just been touched, which requires our more detailed 

 consideration: the dual character of the changes to which a 

 continuum is subject, namely changes in character and changes 



4 Compare A. J. Lotka, Am. Jl. Sci. 24: 216, 1907, the first paragraph of the 

 summary. 



