4 lotka: discontinuous evolution 



try this continuity shows itself on the one hand in the so-called 

 "phases," on the other hand, in a somewhat different form, in 

 the "chemical individuals," i.e., elements, compounds, dissociates, 

 associates, etc. Quite generally such a continuous portion of a 

 discontinuous system shall be called a "continuum." 



Now, aside from the continua known to us in the field of physi- 

 cal chemistry, there are other material aggregates of a very differ- 

 ent kind, which display the same continuity, each within itself, 

 while each is fenced off from the others of the same system by a 

 discontinuity: the biological species are of this character. 



The term "species" is here used provisionally, as being the 

 word in our existing vocabulary which most nearly expresses my 

 meaning. For the sake of exactitude and to avoid conflict with 

 biometricians, who have appropriated the term "species" for 

 use in a more restricted sense, it will be preferable to employ some 

 other phrase, such as "kindred-group," to denote a group of 

 organisms that stand in blood-relationship to one another, either 

 actually or potentially. 2 



It is worth while to note in passing, that the cause of the con- 

 tinuity within a kindred-group lies in its mode of growth: A 

 germ of the parent-substance serves as the nucleus for the forma- 

 tion of the young individual, which, by heredity, resembles its 

 parent. This is what Wo. Ostwald 3 has called " autocatakinetic 

 growth," in analogy with the autocatalytic growth of the solid 

 phase upon a crystal germ introduced into a supersaturated solu- 

 tion. 



Two other types of aggregates deserve brief mention. In the 

 beehive, the anthill, or a human community we have instances 

 of a "social continuum." Such a continuum comprises a number 

 of different social elements joined together in a definite, though 

 not invariable proportion, a proportion essential for the proper 

 functioning and life of the continuum. Such an aggregate also 



2 Barren hybrids, such as the mule, are here to be left out of account ; in nature 

 they will presumably never number more than a small proportion of the total of 

 the crossed groups. 



3 tJber die zeitlichen Eigenschaften der Entwickelungsvorgange; published by 

 W. Engelmann, Leipsic 190S, in the series " Vortrage und Aufsatze uber Entwicke- 

 lungsmechanik der Organismen," edited by W. Roux; p. 36. 



