williams.] BIONIC VALUE OF FOSSILS. 129 
organic vigor expressed by the preservation of the individual life constitutes a 
bionic unit of simplest or lowest rank; the individual, therefore, is an organic 
unit of monobionic rank. How many individual lives are possible in the life- 
history of a species we at present do not know, but we do know that the bionic 
value of the species (or, strictly speaking, of specific characters) is of an entirely 
higher order than that of the individual. To be more concrete the individual, the 
species, the genus, etc. , constitute organic units of consecutively higher and higher 
order of bionic magnitude, which statement may be tabulated in the following 
way: 
Bionic values of the several categories of classification of organisms. 
Individual : a monobionic unit. 
Species fc . . .. _ a dibionic unit. 
Genus a tribionic unit. 
Family a tetrabionic unit. 
Order a pentabionic unit. 
Class _ : a sexbionic unit. 
This actual dibion may be compared with the molecule in the 
atomic theory, for the theoretically simplest unit of the series (the 
monobion) is expressed by the time equivalent of an individual life 
from germ to death — i. e., the life period of the individual. 
In the fossil individual, therefore, we find no evidence of the time 
value of individual development. The vigor which is characteristic 
of each individual of the species at the time may be expressed by the 
numbers of individual fossils found buried together in the same rock 
layer. 
Even this actual number of specimens in a rock layer is not a cer- 
tain test of individual characteristics when taken alone, because the 
conditions of preservation, we must believe, very greatly modify the 
number of individual specimens preserved in the rocks. In order to 
use a number of specimens as an expression of bionic value, the num- 
ber must be in relation to the number of other species preserved at 
the same time under the same conditions. It is the relative abun- 
dance or rarity of a species in the local faunule list alone that is of 
value, just as in the analysis of a mineral the percentages of the com- 
ponent elements are significant, not their amount. 
So far as fossils are concerned, the individual is recorded only by 
its dead remains, and the number of individual fossils of the same 
kind found together in the same faunule may stand for a measure of 
the bionic value of that kind in the particular aggregate of species 
making up the faunule. The larger the number of individuals the 
higher the bionic value of the species relative to the other species in 
the combination. Those species, therefore, which are represented by 
the greater number of individuals in a faunule constitute I he dominant 
species of the particular faunule. The adjustment of equilibrium 
among the species with each other and with the environmenl is such a 
complex and delicate matter that it is preserved for each faunule for 
Bull. 210— 03, 9 
