williams.] BIONIC VALUE OF FOSSILS. 127 
taxonomic classification, viz, species, genus, family, order, class, 
branch. 
Out of these several terms which have actual visible expression in 
nature (viz, difference in form, expressed in terms of species, genus, 
family, etc., in systematic classification; difference in generation, ex- 
pressed by number of individuals of a kind ; and number of genera- 
tions following each other without specific modification) may .be elab- 
orated a means of expressing the relative values of living organisms 
in mathematical terms. 
These values may be called b ionic, implying the energy values of 
living beings, rather than the values of their mechanical powers or of 
their chemical constitution, since development from germ to adult 
and evolution from one to another specific form are phenomena asso- 
ciated only with living organisms; and the term bion may be used to 
express the idea of such a unit of vital force. 
To distinguish this mode of expressing the energy peculiar to living 
organisms from the other modes of energy expressed by machines 
and in chemical reaction of nonliving bodies, the energy may be 
spoken of as bionic energy. It is evident that the bionic energy of 
organisms greatly differs for different organisms; but it is not yet 
known that the differences may not be actually an expression of the 
number of generations through which the ancestors have passed, and 
thus actually may indicate, mathematically, the true bionic value of 
the species or race at the stage in which it is examined. 
THE TERMS "SPECIES," "RACE," AND "GENERATION." 
In order to discuss this problem, we are forced to use the term species 
in a somewhat special sense. Species, when contrasted with individual 
and genus, refers to an aggregate of individuals possessing like mor- 
phological characters. But when we describe a fauna as composed of 
ten or twenty or a hundred species, species is used in a different sense. 
We are not dealing with the aggregate, but with the specific charac- 
ters. Each individual is then a particular species or belongs to a par- 
ticular species. Moreover, each individual in this latter sense is not 
only a species, but a genus, family, and class. 
Bearing in mind this distinction, we find the individual to be an 
aggregate of cells, parts, and organs, and the particular way in which 
these cells, parts, and organs shape themselves in the adult deter- 
mines to what species and genus the individual belongs. But the 
individual also starts as a germ and becomes an adult, and as an indi- 
vidual dies, i. e., loses its individuality. The individual, thus, is a 
temporary expression of the species, and in considering time values 
it is necessary to make distinction between the species as individuals 
and the species as a race. 
The species continues to live after the individual representative of 
it has perished, and species as a time measure is better expressed by 
